Each entry you will add on your device will appear on a list.
To identify each entry, you can set some of your question answers to be part of the entry title (up to a maximum of 3 for either a form or a branch)
For example, let's say you have 3 questions like:
What is your name?
What is your age?
What is your date of birth?
If you set all these questions to be a title, you will end up with a list of entries like:
Mirko 30 22/05/1977
John 18 24/01/1990
Other place where the title is useful is when viewing entries on the server.
On the above screenshot, for the project Bestpint the question "What is the beer name?" is set as the title.
For the entry, the answer was "La Blanche" (a very good French beer) and as you can see, the title is set on the entry popup and in the left sidebar, as a header.
To set one of your questions as title, just select the question inn the formbuilder and check the option on the right panel: