Additional functionality.
WHAT THEY ARE
Modules adding capability: image processing, encryption, database drivers, compression, character handling.
WHY THEY MATTER
Applications require specific extensions.
A missing one produces an error naming the function it needed.
COMMON ONES APPLICATIONS NEED
Image processing, for resizing uploads Character encoding handling Compression Encryption Database drivers XML handling
HOW TO ENABLE ONE
cPanel, PHP selector, extensions.
Tick the extension and save.
HOW TO KNOW WHICH YOU NEED
The application's requirements page.
Or the error message, which names the missing function.
WHAT TO ENABLE
Only what you need.
Every extension loaded consumes memory on every request.
WHAT NOT TO DO
Enable everything to be safe.
That slows every request for no benefit.
IF AN EXTENSION IS NOT AVAILABLE
Open a ticket and ask.