A phylum (plural: phyla) is the third highest rank used in the biological taxonomy of all organisms. The second rank is kingdom. And the highest is domain. However, since genome analysis, groups of phyla have been put together based on evolutionary relationships. These are informal, not part of the standard classification.
Phylum is Phillip in the mnemonic "Dumb King Phillip Came Over From Great Spain", or something similar.
Phylum Facts for Kids. Homework Help - Kiddle Encyclopedia.