A background (also known as a class) is your character's occupation, what they have learned prior to entering the Dungeon. Your background determines your starting skills, stats, equipment, and (in the case of religious backgrounds) your god.
- List of backgrounds
- List of all background and race combinations
- Background and race combinations for beginners
Backgrounds & Difficulty
As one might expect, some backgrounds are easier than others, at least to begin with. The best ones for a beginner are probably Gladiators, Fighters, or Berserkers (who are also a religious class). If you would rather play a mage, try a Conjurer.
Note that Priests are not necessarily the best religious background for a beginner. Berserkers have an easy early time with their berserk ability. Death Knights and Abyssal Knights may be easier, as they start with more combat skills .
Note also that almost every species can and should convert to a god in-play, once you find that god's altar. Indeed, a guaranteed area - the Ecumenical Temple - was designed to facilitate exactly this strategy. Many gods do not have backgrounds to represent them, so you may decide it best to pick a non-religious background, so that you will be free to join one of the "non-starter" gods.
Classes in Crawl
An important difference between Crawl and most other roguelikes (and indeed other video game RPGs) is that your background is only your starting package, not an advancement path that is set in stone.
Crawl was designed to give you a lot of flexibility with how your character develops as they grow, and it does this by giving you a free hand to distribute your experience between your skills however you see fit. Your chosen class has no direct impact on this; it only gives you a starting point to move forward from. Your choice of species, however, can make certain skills easier to learn than others, and your class does determine your starting stats which make certain play styles more or less viable.
For example, your Fighter could potentially learn spells until they look more like a Wizard, build up their Stealth and Stabbing until they're basically an Assassin, take up worshiping a god and gain divine favor (and invocations) like a Priest... or just keep bashing monsters and wearing heavy armor and making your Fighter a more skilled Fighter. As a fighter, your high strength may not contribute as much to these paths as high intelligence or dexterity might, but the choice is there.