'A Slide is a shoe that is backless and open-toed, essentially an open-toed mule. Slides can be high-heeled, flat-heeled or somewhere in between, and may cover nearly the entire foot from ankle to toe, or may have only one or two narrow straps. The term is descriptive in that this shoe is easy to 'slide' on and off the foot when the wearer wants to do so.' Wikipedia
I'm a bit of a fan of a Slide / Slider, i had some great bejewelled H&M ones last summer and i loved them. They are perfect for when you are super pregnant and can't reach your foot to do up a sandal or if your feet have swollen up and you can no longer fit them in any other shoes.