It is a brand name, but there are fake crocs too: Crocs shoes vs. fake Croc shoes? - Yahoo! Answers
Is "crocs" a type of flip flops, or just a brand name? (It comes from crocodile, I guess.)
What is the name for a type of flip flop which is covered in front?
As Birdeen mentioned, "Crocs" are a brand name of shoe/sandal. Not quite flip-flops, although they do tend to make that flip-floppy "slap" noise on your heel when you walk. As for a flip-flop with a covered front, there are many different names, depending upon the specific design of the shoe....sometimes even bedroom slippers fit that description.