Casual Lolita is simply a term used to describe an outfit that is toned down for more casual wear. They often favor cutsews over blouses, petticoats without a lot of poof, and minimal accessories and styling. Many times tee-shirts with cute, Lolita appropriate, prints are worn with Lolita skirts to make a Casual Lolita outfit.
Any style of Lolita can have a Casual Lolita counterpart to it.
Casual Lolita is often confused with Otome because the styles can overlap a bit.