In the game you play as a single monster hunter, there are 5 hunter classes. The classes have different advancement tracks and equipment restrictions. Some hunters can bring hirelings, but only up to a max of four. I can go into detail about the classes if you want but overall you have.
Guild Hunters: The standard hunter, can use any equipment, hire anyone, and gains guild rank over time giving them special equipment and perks. Have to pay guild fees after every hunt.
Monks: Utility class, can't have spirit guides, but have abilities that focus on self healing and buffing. Also get bonuses for fighting when heavily wounded and have to give up any loot on the battlefield to allies. Can the highest stat ceilings.
Shaman: Support class/wizard, not recommended for solo play. Can only use light armor and can't use great weapons, spears, or bows. Their abilities range from healing, stealth, reviving the dead, and magic bolts.
Lone Wolves: Can't use any followers, their abilities focus on killing really big monsters and stealth, letting them outflank, redeploy themselves and avoid ranged attacks, can't have any hirelings.
Eagle Knights: Tengu, can only use light armor but can fly. Gain buffs by killing specific enemies that carry through the campaign, most mobile hunters, can't have hirelings.