There are a total of eight character types in Resident Evil Outbreak, each representing one of the eight primary characters.
Differences between File 1 and File 2
An alteration was made for the standalone expansion pack, Resident Evil Outbreak File #2, where any character of any type could be used in-game, so long as it wasn't the same character. In the original game, a character was representative of its type - George Hamilton could not be used if Sean already was, for example.
Kevin-type characters are agile, and carry the 45 AUTO FOR KEVIN as their personal item in their special Inventory slot. Kevin-types have the ability to kick.
Mark-type characters represent the muscle of the team, though they are balanced by their slow speed. These characters are preferred with melee weapons like the IRON PIPE, as their special move involves a powerful swing. Some objects can only be moved by Mark-type characters, such as the SWAT van in the RPD's underground parking garage. They carry the HANDGUN FOR MARK.
Jim-type characters are more intuitive than others, and can predict where items may be scattered in rooms before they get there (represented by "?" marks on the map). They can also "play dead" in front of zombies - jumping to the floor and lying still. While this is useful when a group is passing by, it does increase the character type's Infection Rate until they get back up. Jim Chapman, himself has low health and highest Infection Rate of the main cast. All Jim-type characters carry Coin (Jim), which can be flipped to increase chances of landing a critical hit.
George-type characters carry the Medical Set, allowing them to create more powerful health items from whatever is scattered around. These characters also have a "dodge-tackle" ability, allowing them to avoid a zombie as well as fight back. It must be charged for four seconds, however.
David-type characters are experienced with various weapons and can fire handguns one-handed. They can also perform COMBO attacks with knives. David-types are also resourceful, and can create maintenance materials with the Tool Belt, and can fix BROKEN HANDGUN SGs.
Alyssa-types can use the Picking Tool to get past locked doors; draws and safes rather than finding a key - players will need to select from several key options and attempt to open the door repeatedly. Alyssa-types, like the Kevins, can also take potshots with the HANDGUN (and other Handgun-weapons) if they keep aiming for several seconds.
Alyssas perform backwards dodges to evade enemies, and make long ad-libs describing the information they have gathered from files.
Yokos have among the lowest health of the playable cast; they can use a dodge to escape enemies, but this will also knock them to the floor. In File #2, Yoko-types can also push enemies away.
Yoko-types are in the posession of the Backpack, which gives them an extra four inventory slots.
Cindy is the Medic to George's Chemist, and uses her Herb Case to store health items for later. Cindy-types can duck to avoid a zombie lunge, which may make them stagger.