TL;DR version

Play with these commands and you will see the difference:

echo $PS1

export PS1="\w \$ "; clear;

PS1="touch me : "

export PS1="username \w\$ ";

export PS1="username \W\$ ";

export PS1="\W\$ ";

export PS1="[\W]\$ ";

more: https://www.cyberciti.biz/tips/howto-linux-unix-bash-shell-setup-prompt.html