i dont want to confuse more, but im going to keep it short and simple

include(): if you use this function, the file you include, if there is an error on it, the script will not stop, it will still continue to parse your code, but it will generate a Warning message.

require(): with this function, if there is an error on the require() file, the script will stop and the rest of the code will not be parse.

simple right?