If you did a new or clean install of OS X version 10.3 or more recent, the default user terminal shell is bash.
Bash is essentially an enhanced and GNU freeware version of the original Bourne shell, sh. If you have previous experience with bash (often the default on GNU/Linux installations), this makes the OS X command-line experience familiar, otherwise consider switching your shell either to tcsh or to zsh, as some find these more user-friendly.
If you upgraded from or use OS X version 10.2.x, 10.1.x or 10.0.x, the default user shell is tcsh, an enhanced version of csh('c-shell'). Early implementations were a bit buggy and the programming syntax a bit weird so it developed a bad rap.
There are still some fundamental differences between mac and linux as Gordon Davisson so aptly lists, for example no useradd on Mac and ifconfig works differently.
The following table is useful for knowing the various unix shells.
sh The original Bourne shell Present on every unix system
ksh Original Korn shell Richer shell programming environment than sh
csh Original C-shell C-like syntax; early versions buggy
tcsh Enhanced C-shell User-friendly and less buggy csh implementation
bash GNU Bourne-again shell Enhanced and free sh implementation
zsh Z shell Enhanced, user-friendly ksh-like shell
You may also find these guides helpful:
http://homepage.mac.com/rgriff/files/TerminalBasics.pdf
http://guides.macrumors.com/Terminal
http://www.ofb.biz/safari/article/476.html
On a final note, I am on Linux (Ubuntu 11) and Mac osX so I use bash and the thing I like the most is customizing the .bashrc (source'd from .bash_profile on OSX) file with aliases, some examples below.
I now placed all my aliases in a separate .bash_aliases file and include it with:
if [ -f ~/.bash_aliases ]; then
. ~/.bash_aliases
fi
in the .bashrc or .bash_profile file.
Note that this is an example of a mac-linux difference because on a Mac you can't have the --color=auto. The first time I did this (without knowing) I redefined ls to be invalid which was a bit alarming until I removed --auto-color !
You may also find https://unix.stackexchange.com/q/127799/10043 useful
# ~/.bash_aliases
# ls variants
#alias l='ls -CF'
alias la='ls -A'
alias l='ls -alFtr'
alias lsd='ls -d .*'
# Various
alias h='history | tail'
alias hg='history | grep'
alias mv='mv -i'
alias zap='rm -i'
# One letter quickies:
alias p='pwd'
alias x='exit'
alias {ack,ak}='ack-grep'
# Directories
alias s='cd ..'
alias play='cd ~/play/'
# Rails
alias src='script/rails console'
alias srs='script/rails server'
alias raked='rake db:drop db:create db:migrate db:seed'
alias rvm-restart='source '\''/home/durrantm/.rvm/scripts/rvm'\'''
alias rrg='rake routes | grep '
alias rspecd='rspec --drb '
#
# DropBox - syncd
WORKBASE="~/Dropbox/97_2012/work"
alias work="cd $WORKBASE"
alias code="cd $WORKBASE/ror/code"
#
# DropNot - NOT syncd !
WORKBASE_GIT="~/Dropnot"
alias {dropnot,not}="cd $WORKBASE_GIT"
alias {webs,ww}="cd $WORKBASE_GIT/webs"
alias {setups,docs}="cd $WORKBASE_GIT/setups_and_docs"
alias {linker,lnk}="cd $WORKBASE_GIT/webs/rails_v3/linker"
#
# git
alias {gsta,gst}='git status'
# Warning: gst conflicts with gnu-smalltalk (when used).
alias {gbra,gb}='git branch'
alias {gco,go}='git checkout'
alias {gcob,gob}='git checkout -b '
alias {gadd,ga}='git add '
alias {gcom,gc}='git commit'
alias {gpul,gl}='git pull '
alias {gpus,gh}='git push '
alias glom='git pull origin master'
alias ghom='git push origin master'
alias gg='git grep '
#
# vim
alias v='vim'
#
# tmux
alias {ton,tn}='tmux set -g mode-mouse on'
alias {tof,tf}='tmux set -g mode-mouse off'
#
# dmc
alias {dmc,dm}='cd ~/Dropnot/webs/rails_v3/dmc/'
alias wf='cd ~/Dropnot/webs/rails_v3/dmc/dmWorkflow'
alias ws='cd ~/Dropnot/webs/rails_v3/dmc/dmStaffing'