Before moving to the next topic, let's talk about the different types of shell available. When looking at the list of available shells, they fall into two categories: bind and reverse.
A bind shell instructs the target to start the command shell and listen on a local port, allowing the attacker to connect to the target on the listening port. A bind shell is great for local vulnerabilities, for example, when you have already compromised a target machine via a phishing attack and want to leverage a local service to do privilege escalation; however, nowadays it is not suitable for most remote exploitation scenarios because the target is probably behind a firewall.
For that reason, most of the time we will use a reverse shell as our payload. A reverse shell starts a connection with the attacker's machine, in this case, the attacker's machine is the...