In PHP there are three main type of errors:
Notices – Simple, non-critical errors that are occurred during the script execution. An example of a Notice would be accessing an undefined variable.
Warnings – more important errors than Notices, however the scripts continue the execution. An example would be include() a file that does not exist.
Fatal – this type of error causes a termination of the script execution when it occurs. An example of a Fatal error would be accessing a property of a non-existent object or require() a non-existent file.
Understanding the error types is very important as they help developers understand what is going on during the development, and what to look out for during debugging.