Determine methodology for creating project management plan

Hi,

I am studying for the PMP exam and I run into something, that I do not completely understand. Namelly, I met with the expression "methodology for creating the PM plan". What is this in practice? How do you perform this in practice?

Thank you in advance for help! Kind regards.

 If you check PMBOK glossary you can find this term. Its explained there.

 Hi,

I was probably not clear enough: why do I have to state in PM plan, what methodology will I use to make it, since I am already working on it? This is what bothers me. I know, that this term can be found in Glossary, but I would like to know, how does this works in practice ....