This article explains the Multi-line Text block that can be added as a block to design an app.
Click on the block and start editing on the panel that appears on the right side.
This is what appears as the name of the input block to the end-user.
This is the text that goes below the input block to help the user.
This is the value that appears to the user inside the input block. This gives an idea to the user about what kind of details can be entered in this block.
Tick this option if you want the user to compulsorily fill the input block.