What does AJAX mean?
Here is an example of some web applications where the AJAX used:
Autocomplete Search Form
If you use Google to search any term or keyword, then you may know that while typing any keystroke in google search you see a drop-down window showing predicted autocomplete words related to your typed keystroke.
Actually, when typing into the Google search bar, it starts to use AJAX to get common results from the database on each keystroke.
AJAX can authenticate user’s credentials with MySQL database without reloading the whole page. If the user is registered then redirect the user to a home page otherwise display an error with a message “wrong password”.