Misunderstanding the difference between single-threading and multi-threading programming

Question

I have a misunderstanding of the difference between single-threading and multi-threading programming, so I want an answer to the following question to make everything clear.

Answer 1

ruby vs python vs nodejs : performances in web app, which takes alot of I/O non blockingrest/dbQuery will impact alot. and being the only multi threaded of all 3, nodejs is the winner with big lead gap