Metagenomics is the study of microbial communities in their original living places. Metagenome sequencing refers to sequencing the entire genomes of all microbes present in a sample in order to explore taxonomic, functional, and evolutionary aspects.
Metagenomics is microbial community genomics
What is a microbiome?
the complete set of microbes that live in a particular microbial ecosystem: within and on the human body (human microbiome), specific plants (grapevine microbiome), or the oceans (marine microbiome)
includes also the entire collection of microbial genes present in any bacteria of these microbial communities