"I've eaten." means that you ate something earlier and you aren't really hungry now. "I've been eaten." means that some animal or monster l ate you / has eaten you "Have been eaten" is a passive verb construction. :)

I've eaten is Active vioce and I've been eaten is Passive vioce LOL

The other answers are correct, but in real life, if you have been eaten by a monster you're not going to be talking about it! I believe what you heard was more likely a common colloquial pronunciation of "I've been eating" -- sono stato a mangiare.

It's like the difference between 'Ho mangiato' and 'Sono stata mangiata' !

i've been eaten: passive, meaning something or someone ate you. i've eaten: it means you ate something and you finished eating.