There are two main types of spitting: Spitting saliva and spitting phlegm. Leaving aside specific medical conditions, there's no physical reason why most of us need to spit saliva:

Spitting is the act of forcibly ejecting saliva, sputum, nasal mucus and/or other substances from the mouth. The act is often done to get rid of unwanted or foul-tasting substances in the mouth, or to get รขโ‚ฌยฆ Sunday, spitting out an ash cloud that rose to 20,000 feet. He has become famous for spitting out food onscreen. The computer was spitting out train schedules to the moon; He couldn't make sense of it.

The computer was spitting out train schedules to the moon; He couldn't make sense of it.