Sun Microsystems was a company that was best known for making computers and computer programs. They made computers called Sun Servers, which were powerful machines used to serve websites and store data. Sun also sold programs that allowed people to work on computers and do things like write documents, access the internet, and play games. Sun was founded in 1982 and was bought by Oracle in 2010. So, if you ever needed a computer or a computer program, you might have gone to Sun Microsystems.