How Do We Know if We're Doing Moderate Versus Vigorous?

The simplest test in the world is called a talk test. Or if you want to go vigorous, you do it all in 75 minutes. But m how do we know if we're doing moderate verses vigorous? So eddie, sarah jenifer asks on instagram, how can i incorporate exercise into my busy schedule? Is it ocat to work out twice a week on week ends for longer periods of time? Would that be equivalent to working out two to four times during the week?