What is the difference between nil, empty, and blank in Ruby?

beginner

Re-explain

nil: Represents "nothing" or "no value". Only nil object responds true to .nil?
empty: A method that returns true for collections with no elements (arrays, hashes, strings)
blank: Rails addition that returns true for nil, empty collections, and whitespace-only strings

nil.nil?        # true
"".empty?       # true
[].empty?       # true
" ".blank?      # true (Rails only)

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