Citation styles ...
1. There are incredibly many. There is not one standard that is used across all disciplines or even within one discipline.
2. Many professors have a preferred style. Search on the website of their chair / department / ..., or ask for it. If there is one: Keep to the specifications of your profs!
3. If you can choose freely, stick to the decision you made. (You can use APA style, Harvard style, etc. as a guideline).
3 facts and 3 questions while waiting for your profs
Example: APA Style
Which citation style do you use?
This is the best way to go!
First stick to the rules of your profs. If there are gaps, you can look up the details in other styles.
You will not fail because of this - but it may not be the smartest thing to drive your professors up the wall.