They consist of a brown, bearded man, a redhead girl, a blonde, moustached man, and a brunette girl. There is also a non-playable Dog that can die.
Beard is the default character you start with, and starts at the rightmost pier. He wears a blue checkered shirt and blue jeans, and aside from hair color, is near-identical to The Husband.
The Redhead has a yellow sweatshirt with long sleeves, starts near the Bedroom Cabin, and has long black pants.
The Blonde wears a green vest and short pants. He doesn't have a shirt and is thus barechested. He starts inside the Zipline Cabin.
The Brunette wears a red sleeved shirt and dark blue pants. She starts at the leftmost edge, and is the closest in location to the killer's spawn point.
Based on clues retrieved in the map, the four counselors seem to be in the mid-20's, and are coming to renovate Camp Lakeview. After a shutdown left the camp abandoned, these counselors were hired to relaunch the camp.
Not much else from their personality can be gleamed. Their supplies contain beer in their backpack, as well as a bong located in the kitchen. They are also capable of having sex in the bedroom, regardless of who the partners are.
It can be inferred that they have the basic personality of any horror movie survivor, and the player is free to dictate how they act.