Coming from other languages and start to learn ruby, you will find a strange concept in ruby which is Symbols.
Symbols are like strings, except they are code.
Symbols is one of the most basic object you can create in ruby. The main different is that each time you use a string, ruby will create a new object while for the same symbols there will only be one object.
> "string".object_id
=> 70358630335100
> "string".object_id
=> 70358640625960
> "string".object_id
=> 70358644379620
> :a_symbol.object_id
=> 1086748
> :a_symbol.object_id
=> 1086748
> :a_symbol.object_id
=> 1086748
Symbols are mainly used as Hash Key and function parameters