What is the difference between sessions and transactions in Oracle?

A session can start multiple transactions. A session is a session and refers to a connection.
A transaction is an operation unit, either successful or failed, with no intermediate state.
The session can complete multiple transactions.
For example:
A session is like a connection to the database in an application. The connection is closed. This is a session.
A transaction is like executing one or more operations on the database in the program after a session is opened.
The best example of a transaction is to transfer money from an account to another account. The data in the two tables is either completely modified or changed to the original one.
View sessions v $ session
Transaction v $ transaction
These two views are connected through v $ session. taddr = v $ transaction. addr,
Transactions are a feature that separates databases from file systems.