Every dwarf will like at least one type of booze and may like none to several food ingredients. It has been claimed that a dwarf will only get a happy thought from eating food and drinking booze he likes.Verify
A dwarf's preferences (and disliked vermin) tend to feature in artwork the dwarf makes more often than subjects not listed in a dwarf's profile. For example, a mason that likes cows for their haunting moos and absolutely detests bats will make statues of both. This is presumably out of love for cows and horrified fascination for bats.
 Benefits to Productivity
A dwarf working with a material they like will produce higher quality goods. For example, a mechanic that likes olivine will generally make better olivine mechanisms than granite ones. This is most important during embark, when individual personality profiles and skills can be best matched up according to your specifications.
This works less well later with immigrants as it is usually more advantageous to train up the great armorsmith than the novice armorsmith who likes steel.
 Value Considerations
A mason who likes horses will often make statues of one or two horses, or even statues of themselves admiring horses. This can be great if the mason is chronically depressed: surround their bed with images they like, and they will be happier.
If your monarch absolutely detests large roaches, a ☼platinum statue of a large roach☼ in their bedroom will actually give them negative thoughts about their bedroom. This problem can be easily avoided by carefully selecting the statue that is going to be built by e panding the material selection menu. Or just don't build statues but cabinets.
This phenomenon is particularly important when choosing an engraver: although rare, some dwarves like types of vermin that others detest, which can result in things like your rat-phobic mayor's office being filled with masterfully designed images of rats.