Definition & Meaning of "where the rubber meet the road"in English

What is the origin of the idiom "where the rubber meets the road" and when to use it?

The origin of the phrase "where the rubber meets the road" likely comes from the world of automobiles and tire manufacturing. The phrase refers to the point where the tires of a vehicle come into contact with the road surface, which is where the performance and effectiveness of the tires can be tested and evaluated. Over time, the phrase came to be used more broadly to describe the point in any process where theory or plans are put into practice and tested for their effectiveness.