Question

When working in Excel Online, what is it called when you drag the fill handle down to copy data?

Answer 1

It’s called drag fill

Answer 2

Auto fill option is a unique feature which has fill handle which is used to copy. Complete fill, Drag fill and Operation fill are irrelevant and not valid in this context.  

Autofill option has multiple features.

1. It copies data again and again for the selected cell

2. It can generate a sequence for the selected cell

3. It also copies formula, other formatting items along with the text. Even if one want to change after dragging the cell, then it is possible to do so.