A taxon is a single or a group of populations that are classified as a unit on some common basis.
A taxon is basically a unit of classification to assign a hierarchical level based on certain characters or groups of characters.
gymnosperm, Aves, Mammalia, etc are some examples of a taxon.
Taxonomy
It is the scientific study of naming, grouping, and classifying organism based on their characters and phylogeny.
Domain, kingdom phylum, class, etc are some of the classification ranks in taxonomy.
Comparision
Taxa and taxonomy are not the same things.
Taxonomy is the science of characterization of animals while taxa can be defined as the group under which a certain population exists.
Homo sapiens belong to taxa Mammalia, but taxonomy is the broader term such as the Hominidae family to which Homo sapiens belong.
Taxonomy allows the categorization of biological entities in order for common accordance in the scientific community to better understand and work in the respective fields.