TurboWarp blocks
TurboWarp has a section of blocks that allows you to use certain feature that cannot normally be used.
These blocks will not work in Scratch and projects containing them should not be uploaded to the Scratch website (per Scratch Terms of Use Section 4.4). The only exception to this is "is compiled?", which will work perfectly fine in Scratch.
If you don't use any TurboWarp-exclusive blocks, then there should be no issue with making your project in TurboWarp and uploading it to Scratch.
This block is pretty simple, it tells you the last block that was pressed. It's intended to be used something like this:
It's like "mouse down?" but lets you check each individual button.