Forms – how can user add fields?

I have to create a form where the user can click a button and add extra fields. Eg. They enter their name, then click a button to enter a second name for their friends who will accompany them, then if a third friend is attending, click the button again to reveal a third name field and so on.

I’ve done some research but I may be using the wrong terminology as I keep finding pages that are taking about adding fields when the admin is configuring a form.

Thanks in advance!