What's the difference between ln -s and alias?

What's the difference between ln -s and alias?

I just found a workaround for a problem I was having with the subl command
for Sublime Text 3 when the MacPorts version of python is installed. The
instructions say to put a soft link, ln-s to the command line app in your
/bin. That didn't work, so I just opened my ~/.profile and added an alias:
alias="/Applications/path/to/subl". But that begs a new question for me.
What is the difference between these two: alias and soft links?