It's been revealed that there will be three "classes" in STO, as well as three different roles for ships.
The classes are Engineer (Gold), Scientist (Blue), and Tactical Officer (Red). Looks like Tactical is now Red Shirt again for two reasons, Marketing and Culture. With the relaunch of the ST universe, people are now used to seeing Red Shirts as soldiers. Plus, it's always been a dream to beam down with 4 red shirts and start a betting pool who would die first, last, and who would survive.
Here's the basics. Most of this information is up on the STO Wiki page
http://stowiki.org/wiki/Main_PageEngineers
Technician: Focus on buffs and debuffs. Their buffs focus on the entire group, unlike a Scientist.
Fabrication: Uses turrets. Most damage focused career for engineers.
Combat: Manipulates the battlefield for the advantage of the engineer.
Science
Researcher: Focuses on group debuffs, and buffs. Use emitters, to to do this. A researcher is especial helpful in large fleet actions and other pvp opportunities. Their ability to buff a large group also allows them to buff you Bridge Officers.
Scientist: Focuses on single person buffs, and debuffs.
Medic: Heal other players.
Tactical
Soldier: The Soldier is the most damage intensive class. They are the most direct attack class.
Security: Security acts as a tank in typical combat roles. Although Cryptic has said that conventional battle tactics will not be part of STO, security can take the most damage. However they must sacrifice some attack.
SpecOps: Special Operations has the unique ability to stealth. They can sneak behind enemy lines and attack from behind.
These roles are independent from the three classes of ships you eventually have access to: Escort Ships, Science Vessels, and Crusiers.
Escort Ships: These heavily-armed warships are built with the firepower to defend the Federation. Escort vessels are armed to the teeth, fast and maneuverable, which makes them a hard target to hit when they’re moving evasively. They are ill equipped to deal with advanced science or engineering tasks. Their lack of adequate medical facilities will hinder their ability to maintain their crew's health. Fortunately, they are so well armed and armored that their crew's health is seldom threatened.
Primary Role: Heavy damage ship, boasting incredible firepower for its size.
Special: Bonus to damage, speed and maneuverability; can load cannons; bonus to weapon power; extra forward weapon slot.
Examples: USS Defiant (DS9), USS Prometheus (ST:V)
Science Vessels:Although Science ships lack the massive firepower of other classes, their technology grants them distinct advantages in combat. Their advanced deflector and sensors can easily identify and exploit weaknesses in enemy ships and target their subsystems, or even detect cloaked ships. Their deflectors can also be used to aid and repair ally ships, as well as control the pace of battle. These abilities allow them to provide superior fleet support, yet they are more than capable to complete missions on their own.
Primary Role: Fleet support, ally aid, battle control. Specializes in buffs, debuffs and control.
Special: Advanced shields, innate subsystem targeting, innate cloak detection; bonus to Auxiliary power. Cruiser Ships
Examples: USS Voyager (ST:V), USS Pasteur (ST:TNG finale)
CruisersCruisers are generally the largest ships in Starfleet. Their size grants them access to advanced warp cores, which allows them to distribute a large amount of power across their subsystems; a large crew complement, which improves a ship’s repair rate, engineering bay, boarding party effectiveness, and so on; and a large inventory, which makes them great for long distance missions. Cruisers have a large warp core and crew complement. Their abundant resources allow them to adapt well to most situations and get damaged systems back online quickly. Cruisers can also support other ships with their massive power supply and crew. Out of combat, these ships' massive cargo holds and crew make them invaluable when it comes to transporting cargo or colonists, and re-supplying planets, space stations or other ships.
Primary Role: Lots of power; large crew complement provides quick repairs and boarding party tactics.
Special: Large Warp Core (power bonus); large cargo space (inventory); bonus to power in all systems; more weapon slots than Science vessels or Escorts.
Examples: Any ship named USS-Enterprise...
. I was afraid that Boarding would be sort of a tacked on feature rather than an option you could go for a fair bit.
