There are seven initial starting character types. Each Character type has one automatic passive skill, and four skill trees. Each level earned through experience points will give that character one point to spend on one of the skill trees. (This is as of alpha 2) Your character can be any of the classes listed below, male or female, and can be named by you in the beginning.
The current starting characters are your main character which is a level one character of any of the above listed types. In addition to two farm hands, which are level 0 characters.
Lydia: Is one of your friends from your escape. Female Farmhand.
Kaius: Is one of your friends from your escape. Male Farmhand.
There are various other characters from the various towns that are randomly generated. As you increase your reputation in their town they will give you help in some ways.