$HOME- expands to the path of my home folder.
$PS1- the variable that represents my command prompt line.
- Scripts are run in subshells, and nothing is shared "upwards". That's the difference between running a script and sourcing one. A sourced (imported) script is run in your own script's namespace.
- In shell everything is a string.
- Children never touch parent enviroment. It can only if it runs as part of the current process (source, function, alias).