Minecraft RolePlay servers can cover many different themes, anything from Prison servers to medieval RPGs and more.
Playing RolePlay servers?
When playing Minecraft RolePlay or RP servers you can usually pick your Role or one will be assigned to you. It's then up to you to try to do your job as best as you can.
Some RolePlay servers are based on Creative servers where players can do own RPs, but that's not always the case, RolePlay servers can have whole systems or maps and NPCs to provide players with completely different RP experience.
Different RolePlay servers?
Some Minecraft RP servers allow freeplay while others don't, since it could ruin experience of other players on RolePlay server, so if you're joining RolePlay server be sure to check out rules.