Your Shell

By default your shell is the Bourne-Again shell (bash) and it will be the default installation.

This is very minimal and most programmers choose to customise it or even pick an alternative shell.

The alternative shell zsh with oh-my-zsh is easy to get going with which can be installed by running

$ brew install zsh

$ curl -fsSL https://raw.githubusercontent.com/robbyrussell/oh-my-zsh/master/tools/install.sh | sh

This will install a fairly comprehensive and useful set of helper plugins that make using the terminal much more enjoyable.

On top of this zsh is a superset of bash, so the two are largely interchangeable.

You will also need make zsh your default shell.

$ sudo chsh -s $(which zsh) $(whoami)

There is an exhaustive guide here if you get stuck.

Stop and understand

Work through section 1.4, 1.5 and 1.6, 2.1, 2.2 and 2.3 in Learn Enough Command Line to be Dangerous (just before “Summary”).
Install an alternative shell (zsh)
Install some plugins (oh-my-zsh)
Make zsh your default shell