So yes, you may be in a comfortable position (any position sitting, laying down) calming your mind with closed eyes in peace and quiet. Equally you may be walking (walking meditation), be it in woods, at the beach or even a busy road with your mind totally focused to a single point, calm & quiet. Doing something mindfully, from eating to gardening to exercising is also a form of meditation as there is an active focus during the activity at the time.

Meditation can be used by itself as a daily practise as well as part of yoga practise.

Meditation as a practise: Choosing a quiet time in your day, find a space that you can be comfortable and warm and turn your phone and other distractions off. Take a comfortable position, close your eyes bringing the focus to your breath. Soften the mind letting the remainder of thoughts and action lists to pass, leaving behind space and quietness. Every time during the practise that thoughts may come through, acknowledge them and without engaging with them let them be on their way. You can listen to soft instrumental music and use a timer to count the amount of time that you meditate or listen to a guided meditation (there is a variety of apps and online guided meditations to choose from).
Many people use meditation as a form of ending their day and as an expression of gratitude or at the beginning of their day setting a calm positive frame of mind.

Meditation and yoga: in your yoga practise, be it daily, weekly or even at random times, you are participating in a meditation practise. During the hold of a yoga posture your mind is focused on the breath and the posture, practically dropping any form of external stimulation, thought etc. The same applies to moving yoga exercises as the breath and body unify in the motion and one leads the other taking the mind to a still level regardless of the physical motion. The final relaxation (savasana) is the time that meditation is manifested in the physical body.