send
sends a message to an object instance and its ancestors in class hierarchy until some method reacts (because its name matches the first argument).
Practically speaking, those lines are equivalent:
1.send '+', 2
1.+(2)
1 + 2
Note that send
bypasses visibility checks, so that you can call private methods, too (useful for unit testing).
If there is really no variable before send, that means that the global Object is used:
send :to_s # "main"
send :class # Object
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