:city is a symbol — interned name. A quoted city is a string.

Goal

Puts a symbol key vs a string key.

puts :city
puts :city.class
puts "city".class

row = { city: "Nairobi" }
puts row[:city]
puts row["city"].inspect

puts :Nairobi.equal?(:Nairobi)
puts "Nairobi".object_id != "Nairobi".object_id

keys = [:city, :units]
puts keys.inspect