The Renders tab is your history of finished clips. Every time you render or insert a generation, the file lands here so you can find it again, drop it on the timeline, or clean it up later.
The tab lists every render you've made, newest first by default. To narrow things down:
Each render shows its name, a preview with an MP4 or MOV badge and its duration, and a line of its settings (resolution, frame rate, and Alpha for a transparent clip).
Open a render or use its actions to:
Select at the top picks several renders at once, so you can delete them together.
The render history is stored locally on your computer, not in the cloud. Deleting a render here removes the file from disk, so only clear out clips you're sure you no longer need.