New User is a user who is being recorded for the first time in a selected analytics property or reporting period.
It matters because analytics turns marketing activity into decisions. Without clear measurement language, teams may misread performance, overvalue the wrong channels, or miss the actions that actually drive revenue.
Example
A first_visit or first_open event can identify a newly observed user in GA4. Browser identifiers and measurement settings affect recognition, so ‘new’ should not be read as proof that the person has never encountered the business before.