Automatically selects and adds inputs to a raw transaction to meet its output values, adding a change output if necessary.

How is this used?

You're putting together a puzzle, but after starting, you realize you don't have enough pieces to complete the picture. The 'fundrawtransaction' command in the Bitcoin world acts like finding and adding the missing puzzle pieces to your transaction. When you create a raw transaction (the puzzle you're trying to complete), you might not have all the inputs (pieces) needed to match the value you want to send. This command automatically selects from your available Bitcoin, adding them as inputs to your transaction to ensure the total value matches what you're trying to send, including adding a change output if you're sending less than the total value of the inputs.