I'd explain it all to you, but a demonstration would be more useful.
Engineers are technological and alchemical masterminds. They employ turrets, grenades, elixirs, a variety of other impressive devices, and concoctions to overcome their enemies. As an adventurer profession, engineers wear medium armor.
The engineer's profession mechanic is the tool belt. It appears above the profession's skill bar, granting each equipped utility and healing skill a corresponding extra skill. For example, when paired with the Grenade Kit, the tool belt allows a Grenade Barrage; with the Med Kit, it adds a Bandage Self.
With their kits, the engineer can have the most skills available during combat among all professions: Each of the engineer's kits provide a set of five different weapon skills. In addition, two of the engineer's elite skills provide new sets of skills, making it a truly versatile profession.
With an arsenal of turrets and kits, the engineer can also become quite durable when properly prepared. However, this is somewhat offset by the long recharge times of their abilities.
 Special skill types
- Weapon kits — Kits that replace the currently equipped weapon (and their skills) with a new weapon. There are three weapon kits available: the Flamethrower, the Elixir Gun, and the Tool Kit.
- Device kits — Kits that replace the currently equipped weapon with more specialized skills. There are three different device kits in total: the Bomb Kit, the Grenade Kit, and the Med Kit.
- Gadgets — A mixed group of various devices, ranging from Rocket Boots to Utility Goggles.
- Turrets — Immobile allied devices deployed to help defend and control an area. The amount of active turrets is limited by the amount of turret skills equipped. Turrets can be packed up by interacting with them, reducing their next deployment cooldown by 25%, or triggered to self-destruct by using the corresponding tool belt skill. Each turret may also be overcharged by the use of a sequence skill to improve the turret's effectiveness; for example, the Rifle Turret's overcharge skill is Automatic Fire. Each turret skill additionally provides a unique tool belt skill when the turret is not deployed.
- Elixirs — Elixirs often provide random support effects for either the engineer or, if thrown by use of tool belt skills, to their allies as well. These random effects are dependent upon the skill used as the skill determines the pool of possible effects.
An engineer has five trait lines to choose from:
- Explosives increases Power and Condition Duration, and favors use of explosives, especially those of Bomb Kit, Grenade Kit and mines.
- Firearms increases Precision and Condition Damage, and increases effectiveness of rifles, pistols and elixir gun, and ranged combat in general.
- Inventions increases Toughness and Healing Power, greatly increasing durability of the engineer, and grants traits which further enhance defensive play, including turrets.
- Alchemy increases Vitality and Boon Duration, and greatly focuses on the use of elixirs and support and improving general survivability.
- Tools increases Critical Damage and Tool Belt Recharge Rate attributes, and, in addition to providing mixed set of traits, increases endurance gain.
The engineer is an adventurer profession, and thus wears medium armor.
- Rifle — Blast foes out of the way or jump to them with a powerful slam attack. Rifles provide the engineer with the ability to manipulate their position as well as the opponent. With a quick interrupt, piercing ranged shots and a short-ranged bleed to deter foes who come too close, this weapon best suits the engineer who prefers to stay mobile.
- Pistol — Poison, bleed or confuse enemies with variety of ranged shots. Pistols allow the engineer to quickly stack a variety of damaging conditions in a short amount of time. This weapon is ideal for engineers who like to focus on condition damage.
- Pistol — Spread sticky glue on the ground or fire a jet of flames from your pistol, providing further condition damage and the option of immobilizing foes. An engineer wielding dual pistols is the only profession capable of reliably inflicting four damaging conditions.
- Shield — Provides protection from ranged and melee attacks and can be used to push foes back with a magnetic pulse. Can also be thrown like a boomerang for a 2-hit ranged attack. Good for engineers who value defense over pure offense while wielding a pistol.
There are three possible weapon sets for the engineer, who also uses a harpoon gun while underwater. Because engineers are able to switch skills using backpacks and weapon kits, they do not have access to the weapon swap mechanic. It is worth noting that weapon kit skills do NOT draw damage or attribute bonuses from the engineer's equipped weapons, except for equipped sigils.
The following crafting disciplines can create items that are useful to the engineer:
- Weaponsmith — Shields.
- Huntsman — Harpoon guns, pistols, rifles.
- Leatherworker — Medium armor.
- Jeweler — Jewelry.
- Chef — Food.
 Personal story
Engineer technology really developed with the Charr first and foremost. And its  one of the specialties developed by the Charr Iron Legion. When we talk about the Engineer he is very much a Combat-Engineer and good in inventing things that are useful in a combat situation. The Iron Legion is the start of all of this, and the Engineer profession has spread to the other races from there. The People of Tyria have seen it in combat over the past few years and have seen the effectiveness of an engineer. And so you are going to see Engineers of all races although it is a little bit more common to see a Charr Engineer than anybody else. So it all started with the Charr and their technological development.
It is funny actually if you combine our April Fools' jokes like combine the commando and your alchemist. That is almost what our engineer is. *laughs*
— Eric Flannum
- The engineer was previewed under this image until its unveiling on May 19, 2011.
- The engineer is the third profession unveiled that is not present in the original Guild Wars.
- Original concepts for the engineer placed it as a heavy armor class.
- The engineer was the final profession to make it into the eight.
- Many believe this class was inspired by Valve's Team Fortress 2. Specifically, the flamethrower and elixir gun appear to reference the Pyro and Medic classes, respectively. The Guild Wars 2 engineer is also similar to the Engineer in Team Fortress 2, in that they both use turrets, can equip wrenches to melee attack enemies (which can also be used to repair turrets), and the line "Dispenser here!" (a quote from the TF2 Engineer) can be sometimes heard when the Healing Turret is deployed, despite never being referred to as a dispenser anywhere else in Guild Wars 2. The rifle's Jump Shot is similar to the Soldier class's Rocket Jump.
- The engineer is the only profession that does not have any signets.
- Engineer on the official website.
- ^ Guild Wars 2: Engineer - Interview mit Eric Flannum und Jon Peters (english), Wartower.de
- ^ a b Exclusive Interview: ArenaNet's Jon Peters and Jonathan Sharp, Tap Repeatedly