From Curious Expedition 2 Wiki

The Explore is the players chosen avatar, the leader of the party and central member of any given expedition. They are chosen at the beginning of the game and cannot be changed or removed as long as they remain alive. At first, only the Big Game Hunter and Anthropologist are unlocked and available to players, but as requirements are met over the course of play, further explorers are added to the list of options. Each of these explorers has a unique ability that will direct and in some cases restrict how adventures are played out.

The explorer chosen also likely effects which perks are offered upon successful expeditions in order to further guide the player down the intended game play style embodied by the given character type.

The explorer select screen with six of the eight exsploers unlocked as of Alpha 12
Explorers Abilities
Big Game Hunter Ambush enemies for a free attack at the start of combat
Anthropologist Sets optional side quest to meet natives, sleep in villages and similar local population related tasks which upon return grant added fame
Plunderer Taking treasures and valuables from shrines and other native sights grants sanity, however you CANNOT sleep in native villages
Cartographer Sets optional side quest to explore all of the island and visit all the landmarks which upon return grants added fame
Taxonomist Animal skins, teeth and other trophies from non native battles add additional fame upon return
Shennong Herbalist In native villages can, for a small reputation loss, obtain local medical herbs which can be returned for additional fame or used as healing items while in the field. The only explorer who CANNOT be female
Red Flag Pirate ???
Nahua Seeker Same ability as cartographer, but has an additional blue dice, a reduced chance of being spotted by enemies and NO combat abilities making them better suited for a pacifist play through