How do moray eels differ from common eels?

Yes they do.

there not a look a like

Conger Eels by genus grow up to 3m in length, while Moray Eels can reach 4m. Each family has over 150 varieties, so answering this isn't straightforward. However in terms of which family can reach...

Yes moray eels are aggressive if provoked.

I'm pretty sure an awful lot. Go to about the 6th picture...that should give you a guess my friend. :) http://www.animalseatinganimals.com/2010/07/when-morary-eels-feel-pekish-what-do.html