What happens to photos on iPhone when I reset the iPhone?

Resetting the phone erases the photos on the phone.

To avoid losing the photos, you need to have them stored elsewhere – e.g., in a backup, on a Mad or PC where you did a manual import from the phone, or in iCloud Photos – before you erase the phone. How you would get photos back onto the phone afterwards would depend on where you were storing them (other than on the phone).

They are erased and cannot be recovered unless you back up the iPhone......before.....you reset it. Ideally, you would back up the phone to a Mac or PC.

They are erased from the phone along with all the other data on it.