S-Class Jobs are those typically done by members like Erza and Laxus, though they can also be done by lower class members if they are escorted by an S-Class mage. While normal jobs are available for all members, the most difficult ones are reserved for S-Class Mages. The jobs available all depend on the type of ranking you have within the guild. They are Normal Jobs, S-Class Jobs, SS-Class Jobs, 10 Year Jobs & 100 Year Jobs.
There are five types of jobs available in a guild. One can opt to do simple tasks, like helping out townsfolk or escorting cargo, to more difficult tasks of finding relics and journeying to mysterious lands. Most bulletins have information on what is needed to be done as well as the equivalent reward. Jobs have different rewards based on the difficulty of the job.
Most payments are done in Jewels, the currency of Fiore.
Most jobs are only available at mage guilds like Fairy Tail, because most jobs are too difficult for any normal person to handle. One of the rasons why guilds are popular is because they provide jobs to their members.
