Descriptions can be styled in various ways or can be omitted. They are completely optional. You can even have hyperlinks in here.
Descriptions are carried in the actual markup, right below their related images so that search engines can see them. The description element can be separately styled with CSS. In this example, descriptions have a different font-family set.
What a pretty bug!
Flies can be beautiful, too (so long as they keep off my lunch).
Butterflies are free (and so was this image).
I'm almost certain this is a bee.
Is it a moth or is it a butterfly.
This little fellow is very classy for a bug.
This grasshopper is named George.
Are those extra eyes?.
If you know what this bug is, please let us know.
She's obviously looking for something - or someone.