Cyber Security is mitigating and where possible preventing the risk of a digital attack. This can include a physical attack on hardware (physically destroying the data) as well as software based attacks (E.G. using malicious code to destroy data or disrupt a service).
Pen Testing is short for penetration testing and is a process completed by an ethical hacker to find vulnerabilities in a system and offer a way to remediate them.
Encryption is converting data to a format that cannot be read without knowing the key/password used to convert the data. The key used for converting data will need to be supplied to decrypt the data to make it readable. This is a two-way process, encrypting the data and decrypting the data.
Hashing also converts the data to an unreadable format, the difference with hashing is that it is one way and cannot be reversed. This is useful for storing passwords securely in a database, when a user wants to connect to the database they will enter their password which will be converted using the original algorithm that converted the data in the first place to see if the two strings match, if they do match the user is granted access. The benefit of using a hash is that if the converted data was compromised it would not be readable without first knowing the original plain text password.
There are 3 main kind of hackers. Black Hat Hackers are malicious hackers that intend to do damage by exploiting vulnerabilities that they discover. White Hat Hackers (ethical hackers) are normally employed to use their knowledge and skill for the good of discovering vulnerabilities and providing a solution for rectifying them. Grey Hat Hackers sit in the middle of Black Hat Hackers and White Hat Hackers, they will often discover vulnerabilities (normally without the permission of the data owner) and then will try and get rewarded from their discovery. Should they fail to get rewarded from their discovery they may then choose to reveal the vulnerability they have discovered to the wider population such as Black Hat Hackers.