Vipassana Retreat 2015 May (https://www.youtube.com/watch?v=bwAl2ORYpBo)
In the beginning, all yogis pay more attention to concepts – the nostril and the rising and falling of the abdomen, for example. But slowly, they notice the touch sensation, movement, and warmth or cold (reality). When the mind thinks less about the nostril (concept), slowly the nostril (form) disappears.
Reality is what we can experience directly through our 6 senses like seeing, hearing, touching and tasting. Concepts are what the mind can only experience through thinking about direction, shape, form, color, and name – e.g. the hand, or a banana.
For example, breath is a meditation object, not the nostril. We can directly experience the temperature, hardness or softness, and the vibration of the breath.