We've seen the tilde (~) briefly as an 'alias' for your Home directory. But it has a few more disguises.
If a word begins with an unquoted tilde character (‘~’), all of the characters up to the first unquoted slash (or all characters, if there is no unquoted slash) are considered a tilde-prefix. If none of the characters in the tilde-prefix are quoted, the characters in the tilde-prefix following the tilde are treated as a possible login name. If this login name is the null string, the tilde is replaced with the value of the HOME shell variable. If HOME is unset, the home directory of the user executing the shell is substituted instead. Otherwise, the tilde-prefix is replaced with the home directory associated with the specified login name.
Does that clear things up a bit?
Knowing that ~ stands for your Home directory, you can use it with the cd command to quickly move around your system.
There are other obscure uses for it. Visit here if you are curious.