What is a one way street?

A one-way street is a street where traffic is only allowed to pass in a single direction - usually enforced by law.

It is literally a road in which you can only travel in one direction. In a figurative sense, it is used to imply that there is either no 'going back' on a decision that has been made or, when used in the context of a relationship, it describes a scenario where one person is doing all the work or making all the effort while the other is not.

selfish....