what is the metasyntactic variale meaning?

Answer 1

what is ... questions are good candidates for google search:

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

Answer 2

A metasyntatic variable is a temporary variable in any programming language. Sometimes when we intend to test our application before releasing it to public, we use these variables. For example, use of foo , bar in JS and C#.
For General example, metasyntatic variable works as a placeholder and its value changes as development of Application proceeds. Just as we look at a password field we find password written in it, but as soon as we place the cursor on the field the password disappears.