'Sitcom'. What does it really mean?

Sitcom is short (an acronym) for 'Situation Comedy', in which a normal person shows or explains their life (usually a weird or unusual life) in a Comic way. 

Some notable situation comedies are:

Not Going Out (2006-)

Outnumbered (2007-2014)

Miranda (2009-)

The Royle Family (1998-2000, specials 2006-12)

Only fools and horses (1981-2003)

Open all hours (1973-1985)