This line of code fixed a pytesseract path issue I was having but I don't understand how it works, can someone explain how it works

Question

So I was trying to run some code using pytesseract, and I got this error:

 raise TesseractNotFoundError()

TesseractNotFoundError: tesseract is not installed or it's not in your path

There was a post on this site that provided the solution, I added it to my code and it fixed things:

pytesseract.pytesseract.tesseract_cmd = r"C:\Program Files (x86)\Tesseract-OCR\tesseract.exe"

However, I want to understand what exactly this line of code is doing as I don't understand? It looks like it is calling a method on the pytesseract library? I don't understand, is this a line of code that can work with any library? What does the "r" in front of the path of the program file do?