Security
Represents the condition of being safe. Security is often associated with the term CIA (no it’s not what you think).  CIA stands for Confidentiality, Integrity, and Availability

Vulnerability
Security weakness in network, software, hardware, or people that can lead to unauthorized access

Exploit
Tool, code, or method that can be used take advantage of a vulnerability

0-Day
Zero-day refers to an exploit or a vulnerability that is not publicly known or disclosed

Security Threat
An event or activity that exploits a vulnerability to cause harm to the system

Security Risk
The likelihood of loss or damage

Hacker
They are no longer like what you read in security textbooks with all those hat colors. Hackers nowadays are people use their profound computer knowledge to hack and gain unauthorized access to computer systems.

Script kiddy
Intention similar to hackers but not as skillful. Often use rely on exploits and tools created by others

Virus
A malicious computer program that requires user intervention (download, click, execute)

Worm
A more intelligent and complicated form of virus that requires no user intervention. Worm has the capability to automate an attack and infect from one machine to another all by itself

Trojan Horse
A rogue computer program that purport itself as an innocent program

Firewall
Access control device to allow or deny access to a resource

Intrusion Detection System
System that detects security breach and sends alert

Intrusion Prevention System
System that prevents security breach by proactive blocking hack attacks