IMVU is 3D Virtual Avatar Chat. basically, you can dress your Avatar up as anything you want her/him to look like. even as yourself in real life or a character.
IMVU has shops that are basically everything from clothing to furnitures, houses, poses. you use credits in IMVU to buy stuff like mentioned above.
you can even be a furry in IMVU too. pretty much just anything you want is right here in IMVU. if you want to see nude Avatars and so forth, I recommend that you buy Adult Pass (AP) to do so. AP also gives you two rooms free.
if you wish to have credits every month you should buy Valued Internet Person (VIP) (I forgot the VIP name, but I call it Valued Internet Person anyway) here's the catch, you'd have to pay monthly or year.
but having VIP earns you a access to Creator status with Create mode that allows you to make stuff like mentioned above too. plus it also gives you access to ten rooms free.
here's even safetry advice for you. skip the browser offer when you get done with the update for IMVU, it contains a virus/malware program inside. the one you know it as an Search Protect.
free credit surveys and normal surveys of asking for you to sign up also contains virus programs as well.
just on safe side
hope this helps you out!