Difference between ls -l and ll?

On many systems, ll is an alias of ls -l:

$ type ll
ll is aliased to `ls -l'

They are the same.

As noted, ll is often defined as an alias of ls -l. In fact, ls is often an alias itself:

$ which ls
alias ls='ls --color=auto'
/usr/bin/ls

The actual command is ls which above is found in /usr/bin. ll is intended as a convenience, but you cannot rely on it being defined on all *nix systems, so it is good to know what it is really doing.

Ubuntu 12.04, 14.04, 16.04, 18.04:

laike9m@laike9m1:~$ type ll
ll is aliased to `ls -alF'