A drop down list in Excel can help speed up data input and ensure the user has entered a valid entry. If you have only a few choices, creating the drop down can be a quick process.
Let’s say you need a Yes/No drop down in a cell.
You can type the Yes No options directly into the Data Validation dialog. (Data Validation is the feature that creates in-cell drop down lists).
Select the cell where you want to create the drop down. Press, in sequence Alt a v v (don’t hold the keys down).
This opens the Data Validation dialog.
See the image below.
Select the List option from the Allow: drop down and then in the Source: box type
You create extra entry options by separating them with commas eg
Will show three entries.
This technique is useful for entries that won’t change, like Yes No.
If the entries could change you would use a range reference to a list in a sheet. That simplifies maintenance of the list.
Any more than three entries and you would also use a list you have already created in a sheet.
You can access a list by using a range reference in the Source box.
I have written about more complex Data Validations at the links below.