Bad practice to declare names in the standard namespace?

Question

I was looking through the Google C++ style guide, and came across this:

\"Do not declare anything in namespace std, not even forward declarations of standard library

Answer 1

This is saying not to declare your own types in the std namespace. You can use the standard library, but you should do so by including the appropriate header.

Basically, make sure all of your declarations are in your own namespace, not std.