You will encounter three followers on your journey in Sanctuary; the Templar, the Enchantress, and the Scoundrel. The Templar is a heavily armored, tough character that can be specced into a very aggressive damage absorption role or into a supportive healing role. The Enchantress tends to be focused on ranged DPS but can also be specced into a player enhancement role. The Scoundrel is a throwback to the rogue of the original Diablo — a conventional ranged character who uses crossbows but also has more damage options and some light crowd control.
In Diablo II, the hirelings were fairly generic, but the followers are specific characters with their own storylines, their own personalities, and their own place within the world. Overall, the followers are also more customizable; you can itemize them and choose from a variety of skills to augment your playstyle.