Sometimes when meditating and one becomes still enough, a nimitta will appear. Nimitta is a Pali word that means: sign. A sign you are getting into a deeper state of concentration/samhadi and close to absorption. The nimitta is a mind generated phenomena, and varies in appearance and behaviour depending on what is being used for a meditation object . It can involve any of the senses, but for me mostly appears as a visual or tactile sensation. Once the nimitta is clear and strong enough it can then be used as a meditation object itself, which can then take one into even deeper states of stillness. There is often an otherworldly feeling that accompanies a nimitta and they can be very weird but in a good way, and certainly nothing to be afraid of. These deeper states of stillness feel very freeing and healing and one can encounter what is known as original mind which is beautiful beyond description.