What does "serve as [something]" mean?

Native speaker’s answer
Rebecca
If something "serves as [something]," it means that it's suitable for a particular use. It can also mean performing duties for an organisation or country. Ex: The table cloth serves as a protective surface from spilt drinks on the table. Ex: The sofa also serves as a bed when we have people over. => an additional use Ex: He served in the army for two years.