In Star Wars Battlefront 2, there are fourteen well known characters and two more with the new DLC - The Last Jedi. You can unlock these SWBF2 heroes and villains by collecting battle points in the battles. Then these can be exchanged in the menu as a currency, hunters or just heroes and in the next round, the battlefield unsafe until you die.
However, before you have the option on the Hero with Battle Points, you need to unlock it with game Credits. For this you need 5,000 - 15,000 credits. So you have to invest a lot of playing time before you can get to a hero. After all, you will receive 5,000 credits after completing the campaign.
So far, you have the choice of playing one of the following eight heroes:
List of all playable villains in the SWBF2
Captain Phasma (DLC)