Screamo
It's the showing of real pain in an angry screaming way. You can't say a band is screamo just because they scream a lot along the song. This kind of sing is always involved with the emo genre. Like: Melodic Metalcore, Metalcore, Emo-core, Post-Hardcore, Fashionxcore, Metal Punk, etc...

Don't get confused with the Metal bands that tend to scream a lot, is just because they're claiming satan. Emo-Screamo is NOT satanic, and emos don't even have religions because we do NOT believe in anything, if it were like that, we would not wish to die.
Screamo: The vocalist who screams is always singing with a slow vocal singer, one after another or both at the same time. They just try to show the pain for us to identify ourselves with the song themes involved.

Example: Underoath, Alesana, Atreyu, Drop Dead Gorgeous, Emarosa, Emery, Emmure, blessthefall, Static Lullaby, Chiodos, The Red Jumpsuit Apparatus, Alexisonfire, A Day To Remember, Eyes Set To Kill, From First To Last, Mighty Moshin Emo Rangers, etc...