Sva - Visayasamprayoge
Citta - Svarupanukara ivendriyanam pratyaharah.
(with) their own; their respective (Vishaya) objects (Asamprayoge) not coming into
(Sva) contact (Citta) of the individual mind's (Svarupa) own form; nature
(Anukara); the initiating or functioning according to (Ive) as if; like
(Endriyanam) by the senses (Pratyaharah) abstraction (fifth constituent of yoga).
Pratyahara is, as it were, the imitation by the senses of the mind by with drawing themselves from their objects.
The goal of a Sadhaka is to attain the yogic state of Citta Vrtti Nirodha i.e. to plunge in to deeper layers of silence by dropping all the Vrttis, all the distractions. The distractions in wakeful state may be of three types: memories of the past, imaginations of future (or present) and the impressions of the world constantly influencing the mind through the sense organs.
Our sense organs have a tendency to pull our mind outside. Eyes want to see something pleasant all the time, for example. That 'something' is the food (ahara) for eyes. To withdraw the senses from their objects so that mind can rest in peace, is pratyahara.
This happens in day to day life without our knowledge. An absent minded student may spend one whole hour hearing a lecture and listening nothing. The heroin of the great classic 'Abhijnan Shakuntalam' by the Sanskrit poet Kalidas incurs the wrath of Durvasa Rishi by not taking any note of him even though she seemed to be sitting outside her hut with eyes open.
Pratyahara is to withdraw the senses as a master, not by force, but by understanding, with wisdom-as naturally as a tortoise withdraws its limbs sensing any danger.
The memories of past and imaginations of future are to be overcome by Dharana and Dhyana the steps subsequent to Pratyahara.