Pls explain metasyntactic variables clearly

Answer 1

A metasyntactic variable is a meaningless word used as a placeholder in computer science, intended to be substituted by some objects pertaining to the context where it is used. The word foo as used in IETF Requests for Comments is a good example.

https://en.wikipedia.org/wiki/Metasyntactic_variable

Answer 2

it's really just a placeholder word in computer science. In older languages, 'foo' and 'bar' were used, where in python 'spam' and 'eggs' exist.

It really has no more meaning than "Hello World". It's a familiar set of words used as a teaching aid to help you better understand what's happening.