Difference between [:key] and ["key"] in ruby [duplicate]

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• Is there any difference between the `:key => “value”` and `key: “value”` hash notations? 5 answers

I want to know the difference between [:key] and ["key"]. Like when we get params in controller by form. If we iterate them like params[:key] or params["key"]

Both behave same. So what the difference in them if any?

Another thing which I can't differentiate till yet and not get any major difference between

:key => value and key: value

Please tell me their differences