Five Different Ways to Meditate - four of five

Breathing as a point of focus during meditation is another technique used to maintain attention during your practice.

How do you incorporate breathing into your practice?

Count your breaths and notice the sensation it produces.

In this instance, the breath becomes the sole object of your meditation. You observe every nuance of the breath and each sensation it produces: how it moves in your abdomen and torso, how it feels as it moves in and out of your nose, its quality, its temperature, and so on. Though you are fully aware of all these details, you don’t dwell on them or judge them in any way; you remain detached from what you’re observing. What you discover is neither good nor bad; you simply allow yourself to be with the breath from moment to moment.
— MARA CARRICO, Yoga Journal, "A Beginner's Guide to Meditation"

Breath observance is the predominant technique in “insight” or “mindfulness” meditation.