A setup includes restringing, cleaning, lubricating parts, tightening of all hardware, setting intonation, polishing frets, oiling fretboard and fine tuning your instrument to play at its best.
Setups are recommended for new instruments, people new to their instrument, and annually. It’s really hard to learn how to play guitar on a guitar that can’t be played. A good setup will make the learning experience much less stressful and more probable.
CF. Restorations 