Provide a table ID at runtime
To use the Table function cards (such as Create Row), you typically select the Table that the function will operate on by clicking Choose Table on the card.
However, you also have the option to run a flow using a table without specifying one in advance. For example, you could be using a child Flow which gets the table ID from the parent Flow when its running. Or you could be creating a new table earlier in the Flow so you don't know the table ID until the Flow runs.
For those cases, select Provide table ID at runtime. When you choose this option, you will also need to add a value to the Table ID field.