Combine a photo of a cat with a poorly written (bad spelling and incorrect subject-verb agreement are important) caption in sans serif font, and you've got a lolcat. The term is a composite of 'LOL,' which stands for 'laugh out loud,' and 'cat,' and the adorable images the word describes are an Internet phenomenon.
The first recorded use of the word lolcat occurred in 2005 on 4chan, an imageboard website that features cat photos on Saturdays, or 'Caturdays.' But these funny feline photos have been around longer than you think and there's a reason you can't get enough of them.
(via Look At This...)