Under FreeBSD and other unixlike OSes, cd means just what it does under Windows - "change directory." The cd command is built into any version of the Unix shell that you are likely to find.
The notable differences being that under unixlike OSes a space is required between cd and the name of the directory to change to and a forward slash / is used instead of a backward slash \
C:\Windows> cd\stuff (windows) splat# cd /stuff (unixlike)
C:\Windows> cd.. (windows) splat# cd .. (unixlike)
cd by itself will send you to your home directory, as will cd ~. cd - will show you and then change your directory to the last directory you were in, as below:
[dave]@deus /var/log % cd ~ [dave]@deus ~ % pwd /home/dave [dave]@deus ~ % cd /etc [dave]@deus /etc % cd - /home/dave [dave]@deus ~ %
.. up one level, e.g., cd .. in /e/foo will take you to /e/ - previous directory ~ home ~username home directory of the user "username" . the directory I am in. Not used very often with cd but more often with commands.