In yogic Sanskrit, mindfulness is smrti-sādhana, absorption is samādhi, and contemplation is svādhyaya.
Veteran teacher Dr.G.Mohan has wonderful perspective to share on approaching meditation practice through three unique, but equally significant techniques:
The first is Mindfulness in which we maintain a witnessing presence, as an observer of the object or situation. For example, if you are noticing your breath, you are not completely absorbed in the sensations of the breath. You simply remain present as these sensations arise and pass in your awareness, but you remain separate from the breath.
In an absorptive mediation, or Samādhi, we are completely absorbed in the experience, actually losing the sense of the self. The goal here is to actually allow oneself to merge with the object of attention – using the above example, there is no distinction between the awareness and the sensations of breathing.
Both these techniques involve a direct experience of the target of attention.
In Svādhyaya or contemplative meditation, we simply reflect on the experience using our thoughts or words. We are engaging only at the level the intellect, and without directly immersing in the object or experience.
Dr.Mohan maintains that yogis with a deeper exposure to the yogasutra and the study of meditation may realize that mindfulness meditation and absorptive meditations merge at an advanced level, when the yogi finds absorption in awareness itself.
He also emphasises that it is vital to understand that each of these three practices is distinct but essential. One cannot substitute the other, and the guidance for practicing each effectively is different too.

