Does my car need oil?

The oil light came on two or three times yesterday on my W reg Renault Clio, only for a second as I was going round corners. I haven't yet checked the dipstick, will do that at lunchtime. Would the light just mean that it needs more oil? And would I need to drain the existing oil before I put new in, or would I just top it up? And do I need a particular type of oil? Never had to do this before!!