what is a computer security flaw exactly?
Like I know the text book definition and read about it on wikipedia. I want to know how someone spots these like what do they look like and how does one even get to the point where you can see one. like how would I right now go to a website or to some software get to the coding and then find a flaw
It takes a lot of work, and experience. There is nearly always a weakness that can be exploited in any string of code. When a hacker decides to break into a system they will look for that weakness. Because cyber security is improving and always changing, I cant give you a single method for hacking a system. Each hack is unique to the system it is getting into. For example, Google the stuxnet virus.
A hacker will attempt to break a system for a number of reasons. Curiosity, money, espionage, etc. If a knowledgeable hacker is hired to break into a system, it will probably happen. You may also want to check out zero-day attacks.
Hope this helps!