Functional Testing is the testing process primarily used in the development of software where the software is tested to guarantee it’s adhered to all the pre functional requirements.
It is the testing process in which the testing is made to check the non-functional aspects of the software/system are made. The non functional aspects include performance, usability, compatibility, etc.,
Security Testing discovers the known and unknown vulnerabilities in the software application to protect from the malicious attacks from possible intruders, thus making sure that the software applications are free from threats.