Almost literally every part.

Lemme think if some common ones
>you steal money
>you take down whole systems
>you steal data
>I know people who think downloading music is hacking
>you track passwords
>you can get into every account
>you track ip's and blackmail people
>you install/make viruses
>you delete data
>you invade privacy


I'm sure there's more. Most people have no clue

>>16902679
Can you explain what they actually do?

>>16902645
When someone leaves their Facebook account open and a friend posts a status that starts with 'YOU'VE BEEN HACKED'.

>>16902645
Hacking doesn't exist, call it 'cracking'.

>>16902693
Not the same person but here's a few examples:

SQL-Injection is one of the classic ways to hack a databases and because of it all user inputs need to be sanitized properly so users can't just input SQL code in to name or address fields. This needs to be done on a the server because users can modify client side code and the data it sends freely.

Another one is memory hacking, for example in games you kill a few enemies to get score and then you use your memory hacking tools to search for place in memory that contains the same number and simply change it to contain something else like 9001 and suddenly you've set up a new high score in game.

Then there's phishing where you simply try to fool stupid users in to giving you money or their personal information by deceiving them that you're system administrator or something or alternatively fooling them that they have something a lot more to gain. Some of these use fake sites that look just like the original but when user logs in to them the site saves the password and username and redirects the target to the actual site or error or something.

Man in the middle hacking is probably easiest to explain as something where you cut a line between 2 or more participants and add your own system in between and start listening and possibly modifying the data that the participants send out. It's actually one of the reasons why all data should be encrypted online.