How would I make a tokenizer and a token vector for the shunting-yard algorithm?

I’m pretty new to c++, and I wanted to make an RPN calculator (including stuff like gcf, sin, cot, mean, etc), but after some research, I found out I need a tokenizer and a token vector. However, both of those seem to use a bunch of code with enum classes and stuff that I really just don’t understand. Could anyone explain to me in detail what all that stuff is or direct me to some websites or books that can do that?