Ningage wrote: Post-Hardcore are bands that people usually call screamo, but aren't really screamo. Post-Hardcore is an offshoot of Hardcore that goes a little more melodic. It mixes screaming and melodic singing a lot. Examples of Post-Hardcore are Silverstein, blessthefall, Underoath, I Set My Friends on Fire, etc.
Going to expand on this.
Post-Hardcore, while including what Gabe has described here, is a lot broader of a genre. Post-Hardcore is to hardcore punk as post-punk is to punk rock. It takes a lot of influence from hardcore but tried to expand the sound far beyond three angry chords for two minutes. Early bands doing this include Minutemen, Husker Du, Big Black, NoMeansNo, Fugazi, and so on.