Leave off the protocol (http://) and use single quotes around the domain like:
:inet.getaddr('www.google.com', :inet)

The function just need the hostname:

iex(11)> :inet.getaddr('www.google.com', :inet)
{:ok, {142, 250, 185, 100}}

It returns error because you are passing an Elixir String / Binary, while it is an Erlang function expecting argument which is Charlist.

These two types are not directly compatible and you have to convert between these two often when using Erlang libraries from Elixir. Generally charlists literals will be wrapped in single quotes ’ and binaries with double quotes ". You can convert between these with to_charlist and to_string functions that are imported by default everywhere.

So, your example will work if you use single quotes and skip https:// which is a protocol. You should write:

:inet.getaddr('google.com', :inet)
{:ok, {172, 217, 16, 14}}