What does the 'export' command do?

Question

I am a little new to Linux, and I happen to run some commands blindly, in order to get things done. I thought that it will not be a waste of asking these type of questions,

Answer 1

export in sh and related shells (such as bash), marks an environment variable to be exported to child-processes, so that the child inherits them.

export is defined in POSIX:

The shell shall give the export attribute to the variables corresponding to the specified names, which shall cause them to be in the environment of subsequently executed commands. If the name of a variable is followed by = word, then the value of that variable shall be set to word.