What is Remote code execution?
How it works? and How to resolve it?
remote code execution is someone executing code on your host from diverent server. You can block visitors or acces from other hosts to acces/run scripts on your host.
RCE gives one the ability to execute commands on your server either via a URL or netcat etc best way to to protect yourself is fix the application that is vulnerable either by correcting the code or updating the application - if you own the server use mod_security with a decent ruleset to block such attacks.
You can set your php to not allow remote execute in your config.
Remote code execution is just as the name implies, code executing remotely, for instance hackers exploit some remote software listening on a port, usually with some form of buffer overflow, and after it's overflown the contents of the buffer, which can be shellcode are ran and the code is executed within that processes memory. This allows the attacker to download+execute files, add user accounts etc...depending on what privilege the process is running under.