My answer to that is yes, depending on where you are on the pushup scale. On one end, there is strength and on the other there is endurance. Can you perform at least 20 pushups? If so, then you are working endurance, focusing more on mastering the weight than getting stronger.
Can you only perform 5 pushups total? Then the pushups are focusing more on creating strength. Personally I like to use pushups as a cardio exercise most days. How’s that you ask? Well, what is cardio really? I define cardio as high reps of an easier exercise- more or less. So if I can do lots of reps, then the exercise is cardio.
I discuss using four bodyweight exercises as a cardio workout in my bonus report: What’s a better way to do cardio?
This report is also included as a bonus in 1 Minute Cardio 2.0