For reference. The absolute path is the full path to some place on your computer. The relative path is the path to some file with respect to your current working directory (PWD). For example:
Absolute path: 
C:/users/admin/docs/stuff.txt
If my PWD is C:/users/admin/, then the relative path to stuff.txt would be: docs/stuff.txt
Note, PWD + relative path = absolute path.
Cool, awesome. Now, I wrote some scripts which check if a file exists.
os.chdir("C:/users/admin/docs")
 os.path.exists("stuff.txt")
This returns TRUE if stuff.txt exists and it works.
Now, instead if I write,
os.path.exists("C:/users/admin/docs/stuff.txt")
This also returns TRUE. 
Is there a definite time when we need to use one over the other? Is there a methodology for how python looks for paths? Does it try one first then the other?
Thanks!
The biggest consideration is probably portability. If you move your code to a different computer and you need to access some other file, where will that other file be? If it will be in the same location relative to your program, use a relative address. If it will be in the same absolute location, use an absolute address.
When to use Absolute Path vs Relative Path in Python