Campaign Creations

I have just recently discovered that there is such a thing called feats what are feats and are they similar to
achievements just not being viewable ? Or do they unlock some secret or something

They're just for fun. There's one each in Books 1 through 5; some are more obvious than others. The one in Book 3 is probably the most obscure (in fact the only way to get it is to unlock just about everything else-- hence why it's a Feat) while the one in Book 4 is very easy.