This document covers the Python APIs available in the MySQL Shell:

X DevAPI - NoSQL Database API for MySQL and the MySQL Document Store.
ShellAPI - Shell API and backward compatibility API for MySQL Servers not supporting the X DevAPI.
AdminAPI - API for setting up and managing InnoDB Clusters, InnoDB ReplicaSets, and InnoDB ClusterSets.

The functionality of the APIs is exposed through modules and global objects which are automatically available when the MySQL Shell starts.

The mysqlx module contains a complete development API to interact with MySQL Servers using a session through the X Protocol.
The mysql module contains a lightweight development API to interact with MySQL Servers using a classic session.
The dba global object enables you to administer InnoDB clusters using the AdminAPI.
The shell global object gives access to general purpose functions and properties.
The session¹ global object is available when a global session is established.
The db global object is available when the global session is established through the X protocol using a default database.
The util global object that groups miscellaneous tools like upgrade checker and JSON import. ¹ The session global object might be either a ClassicSession or a Session object depending on whether the global session was established using classic MySQL protocol or X protocol respectively. For additional details look at the connect function in the shell object.

For more information on the functionality these APIs provide see the following documentation:

The Using MySQL as a Document Store documentation explains how to use X DevAPI to achieve a NoSQL-like MySQL database.
The X DevAPI user guide provides details about and usage examples of the X DevAPI.
The InnoDB Cluster user guide explains how to use MySQL Shell and AdminAPI to set up and administer a highly available InnoDB Cluster.
The Group Replication documentation provides detailed documentation on the replication group which InnoDB Cluster utilizes.