In the passive reconnaissance stage, the tester gathers information about the target using open-source intelligence (OSINT), like information from social networks. It does not use tools to directly probe the target system.
In the active reconnaissance stage, the tester actively probes the target system to collect and analyze the responses. Example: network scanners (like nmap) and vulnerability scanners (like nessus) are used in this stage.
After the tester has collected the vulnerabilities that she is able to discover on the target system, she exploits one of these vulnerabilities to gain access to the system. This first exploitation is called inital exploitation and the vulnerabilities that the attacker can initially exploit are part of the attack surface of the system. It is important to keep this attack surface as small as possible, to reduce the possible entry points for an attacker.
The tester has now gained access to the system, but right now it has tipically few rights. For example, it has exploited a misconfigured Guest account to enter the system. Now that it is inside, the tester uses escalation of privilege techniques to gain more rights on the exploited system.
The tester has compromised a system and the higher its righer, the more are the actions it is allowed to perform. Pivoting is the practice of using the exploited machine to reach other machines inside the same network. Example: the tester has compromised the Internet-facing Web server. At this point, it launches an attack from the web server to gain access to the database server.
At this point the tester has successfully conducted the exploitation of the target devices. Persistence means setting up remote access to the exploited devices. This may be achieved by creating a backdoor on the system.
In a black box penetration test, the tester has no prior knowledge of the environment to be tested. This test simulates an attacker with no initial knowlege (like an external one).
In a black box penetration test, the tester has full knowledge of the environment to be tested. It know which devices are present inside the network, the network topology, the OSes and the applications installed and so on. This test simulates an attacker with full initial knowlege (like an insider with high privileges).
In a black box penetration test, the tester has partial knowledge of the environment to be tested. As an example, it may know the devices in a subnet, but the path to reach other target may be unknown a priori. This test simulates an attacker with partial initial knowlege.
The main difference between vulnerability scanning and penetration testing is that, while both discover and document vulnerabilities, penetration testing actually exploits them. In this regard, it is much more intrusive and can even cause interruption of service of the target system.