During one's career in academia, in the STEM fields of research at U.S. universities, what are typical examples of academic politics? What are some typical examples of "academic politics" that professors face in academia?  

Does academic politics mainly affect younger professors?  

I've seen the term "academic politics" come up in some past questions on this site, but I realize that I don't actually know what it means - I just know that it is something that can cause students to quit PhD programs and professors to leave academia.  

(I kept the question specific to STEM fields of research at U.S. universities, just in case my question would be too broad without it.)
Almost every aspect of the job has politics invovled. Who teaches which classes, on what days and in which rooms. The distribution of TA support. What committees you serve on and what roles you play on those committees. Which lab space and office space you get. Rotation of sabbatical and research leaves. If there is any departmental funding, how it is spent. The hiring of new faculty and the admission of PhD students. I have even seen fights over what types of pens are kept in the supply closet.

Generally as a new faculty, there are certain thing in your contract and other thing agreed to verbally and in emails. In toxic environments, and even in some good environments, these things will come under attack. Even things in you contract will come under attack from colleagues who want to take advantage of you.

That is not to say it is all bad and not all colleagues will be out to get you. In good departments there will be more people looking out for you and only a handful of bad apples.