How do I find command list that are used in a given library(i.e. gpstiny or gsm)

I am new to programming but have an understanding of how things work, and the Arduino references have helped me greatly. Regarding libraries put together for different products(i.e. LCD, GPS, GSM, etc.) like the gpstiny library or any others out there, how do you know or where can you find the commands or functions the library includes to take advantage of the library? I have found some based off of code I deciphered or other tutorials but is there a way to dissect the library or how does that work. If I can figure this out I may be able to actually build something.

Thank you in advance!!!

how do you know or where can you find the commands or functions the library includes to take advantage of the library?

If there is no documentation, open the header file, to see the list of methods that the class has. You may need to look in the source file for clues as to how to use the methods.

Well written libraries will often come with documentation and working examples to explain and demonstrate how to use them. You might sometimes have to look at the library's header files to find what the public interfaces are, and maybe even the implementation to understand what they do so you can guess how they're intended to be used, but that should be the exception rather than the norm.