A drop-down list is a list of options that appear as a menu in a cell in a Google Sheets spreadsheet. When you enter a value in the cell, the drop-down list will show the options that are valid for that cell.

To create a drop-down list in a Google Sheets spreadsheet:

1. Open the spreadsheet and select the cell where you want to create the drop-down list.

2. Click on the Data menu and select Validate.

3. In the Validate dialog box, select the Drop Down List option.

4. Click the Add button and enter the list of options for the drop-down list.

5. Click the OK button.