What is "pom"
The pom.xml is the file that describes the characteristics of a project Maven.
Briefly, this file may contain:
Build Settings
Artifact Definitions (version, id, etc)
Plugins of the Project
Properties of the Project
Relationship between modules
Dependency management
There are other attributes that can be defined by pom.xml.
To see the full list of these attributes and understand, in detail, how each attribute works, read the guide of pom.xml on the Maven website.