Unit-of-Work Design Pattern vs Transactions

Hello devs: 

I started reading up on Unit-of-Work (UoW) patterns for example here: Martin Fowler on the Unit of Work Pattern.
Frankly, I am not sure what the difference is between UoW and the concept of a database Transaction.

Most simple SQL operations are auto-commit so there is no need for the developer to explicitly bracket the code within a transaction.

With multiple SQL operations (such as a bank transfer or a purchase of a shopping cart full of products) the developer needs to bracket the operations within a Transaction and they either 1) all succeed (Commit) or 2) all fail (Rollback).  

These are relational database principles that have been around for a long time. 

So, my question is what is UoW adding to this principle or how does it differ?

Trey H.