Samadhi, the fourth quality of practice (according to Yoga Sutra 1.20), is variously translated as contemplation, stillness of mind, all-consuming focus, and absorption. The first three qualities of practice are related to Samadhi. You must have faith that getting quiet takes you somewhere you want to go (sraddha). You must exert the necessary effort to find it (virya). And you must remember that quietness is always there (smriti), that in fact, it is your essence.
Samadhi is also the eighth limb in the eight-limbed path of yoga. So we can think of Samadhi as both the result we are seeking and the means to the end. We end up with a quiet mind by regularly quieting the mind.
And so we strive to cultivate this stillness of mind not just in formal mediation but all the time, in the midst of the quick pace of daily life. Find those moments of stillness in the day to day, drinking tea in the morning, on your commute, while washing the dishes after dinner.
I hopscotched around South Louisiana last week, visiting various members of my family over the holidays. Along with being a whole lot of fun, it was hectic, and chaotic, and noisy, and tiring. But on the drives between each stop, I spent at least five minutes just breathing, being present, looking at the sky out the windshield, letting go of thoughts. Donna Farhi describes the quiet mind as the blank background on a strip of film. We see the images going by at warp speed, but if we slow down, we can see that each frame lays on a background that is neutral, spacious, and open.
Connecting to that space is Samadhi.