Raise Dead is an iconic spell popularized by, if not introduced in, Dungeons & Dragons. It is essentially the /tg/ equivalent of a respawn, a spell that can be used to bring a deceased adventurer back to life and allow a player to continue playing their original PC, instead of having to generate an entirely new one. This is actually a contentious little spell, because some DMs disapprove of it on the basis of it lowering the overall stakes, both in the sense of potential impact on world-building and their (or their players') investment in the game.
Traditionally, Raise Dead is part of a small sub-family of spells, usually accessible by Clerics. In addition to beefier versions like Resurrection and True Resurrection, it also has a cousin in the form of Reincarnate and Clone. Raise Dead is limited by aging the caster or, in 3rd edition onward, requiring an expensive diamond.
In Eberron, Raise Dead is limited by the fact that Clerics capable of casting it, much less willing to do it for hire, are rare and the two major religions, The Sovereign Host and The Silver Flame, dislike casting it. Instead, adventurers would have to get a more costly Resurrection from House Jorasco or seek the aid of one of Eberron's less mainstream religions, which is quite likely to result in you getting screwed.