Why is useful to have a atom type (like in elixir, erlang)?

Question

According to http://elixir-lang.org/getting-started/basic-types.html#atoms:

Atoms are constants where their name is their own value. Some other lang

Answer 1

Atoms are constants with itself as value. This is a concept very usefull in distributed systems, where constants can be defined differently on each system, while atoms are self-containing with no need for definement.