It depends (but only the ones related to it).

There is the base game, ARR and its expansions Heavensward, Stormblood, Shadowbringers and Endwalker.

In ARR, you unlock the coil raids in sets of 4-5. You must complete the last one in order to continue the quests to unlock the next set.

In each expansion, the raids for that expansion must be unlocked one at a time and then completed in order to progress to the next. There are 12 raids in each raid series (for Alexander, Omega, Eden and soon Pandaemonium) and those 12 need to be done in order. They were originally released in sets of 4, so every 4 raids, you can then visit a certain location to unlock the Savage versions, which are the high-difficulty versions. Once you beat the 4th floor of certain Savage sets, it sometimes allows you to unlock an Ultimate raid, which is an even higher-difficulty raid that needs 7 regular friends to do it with.

There are also Alliance Raids. These are 24-person raids, but they are casual content and quite easy because the amount of healers there means you'll be revived if you die. There are 3 per expansion, and the 3 must be done in order.

There are also some raids in Bozja from Shadowbringers, which requires the Stormblood Alliance Raids to be completed and then a whole lot of its own content, before its large-scale (up to 48 person) raids unlock. There is one large-scale raid in Eureka from Stormblood as well, which requires going through 4 grindy zones first.