Robotic Process Automation or RPA is a capability that allows you to carry out tasks on a computer just like a human would.
The best way to visualize would be to think of a person working on his computer and doing his daily job by clicking through computer screens, sending emails etc. Now, what if the computer clicks through, enters required data and performs the same work automagically? That is what RPA enables.
Let us say that Bob is responsible for processing invoices in SAP. He would log in into SAP, go to the specific transaction and enter the invoice details one by one. Now if RPA were to carry out the same task, it would log in automatically and carry out the tasks without Bob having to do this repetitive work.
Watch this(an RPA tool) which shows exactly how RPA performs that operation.