Absorption is a sign of concentration in meditation. It is a bit like when watching the TV and everything else disappears except what’s on the box – you were so engrossed in it you might say “that movie was absorbing”. When you practice single-pointed focus, there is a similar process that happens.
At first, you’ll not hold onto the ‘object’ of meditation
For convenience I’ll just mention ONE such object although there are many to choose from. Let’s say your ‘object’ for single-pointed focus meditation is the sensations at the nostrils. When you place your awareness there, you notice the air going in is a little cooler then the warm air of the out breath. You may notice other sensations too. These sensations (and temperature) is the ‘object’ of your meditation – the thing you are focusing on.
As the process of bringing your awareness to the object, then noticing your mind has wandered to something else (thoughts, other body sensations, sounds, etc), and bringing your mind back to the object again…. as this process progresses, you will be aware that the mind will stay upon the object for longer periods, but also the object will get closer.
The object will appear to get closer…
… until you are almost on top of it (almost absorbed into it). At this point, you may be aware that your body has disappeared, as has everything else except the object. You will also experience a certain amount of suppleness in your body which makes meditation easier.
This process of everything disappearing (including the disappearance of all sensations of your body) except the object, and the comfortable suppleness experienced when one gets to this stage, is called ‘absorption’.
It may take months of meditation practice before one attains any absorption at all, but it is very much worth the effort. For one, when you can become absorbed in meditation your meditations are hugely more pleasurable due to the suppleness induced. You have also taken a bit of control away from the mind and are well on the way to training it to do your bidding. It also means there will be less time required to be in solitary retreat to attain tranquil abiding (and the FULL control over your mind) if you ever want to do this.