To the best of my knowledge.
Once a player gets a kill in raid instance, they get locked to that instance for that level. I think they can continue to do that instance over and over if they want, but they are only eligible for loot on the first kill for any particular boss. ( I could be very wrong on this point )
LFR, normal, heroic, and mythic all have independents lock outs so you can clear all 4 levels once and get loot from every boss.
If your asking about completely different raids, yes every raid and raid difficulty has it’s own lock out.
You can look at your calendar in game and it will tell you when locks expire if your locked to anything.