'hindrances', are 5 qualities which are obstacles to the mind and blind our mental vision. In the presence of them we cannot reach neighbourhood-concentration (upaca^ra-sama^dhi) and full concentration (appana^-sama^dhi), and are unable to discern clearly the truth. They are:
1. sensuous desire (ka^macchanda),
2. ill-will (vya^pa^da),
3. sloth and torpor (thi^na-middha),
4. restlessness and scruples (uddhacca-kukkucca), and
5. skeptical doubt (vicikiccha^; q.v.).
In the beautiful similes in A. V, 193, sensuous desire is compared with water mixed with manifold colours, ill-will with boiling water, sloth and torpor with water covered by moss, restlessness and scruples with agitated water whipped by the wind, skeptical doubt with turbid and muddy water. Just as in such water one cannot perceive one's own reflection, so in the presence of these 5 mental hindrances, one cannot clearly discern one's own benefit, nor that of others, nor that of both.
Regarding the temporary suspension of the 5 hindrances on entering the first absorption, the stereotype sutta text (e g. A. IX, 40) runs as follows:
"He has cast away sensuous desire; he dwells with a heart free from sensuous desire; from desire he cleanses his heart.
"He has cast away ill-will; he dwells with a heart free from ill-will, cherishing love and compassion toward all living beings, he cleanses his heart from ill-will.
"He has cast away sloth and torpor; he dwells free from sloth and torpor; loving the light, with watchful mind, with clear consciousness, he cleanses his mind from sloth and torpor.
"He has cast away restlessness and scruples; dwelling with mind undisturbed, with heart full of peace, he cleanses his mind from restlessness and scruples.
"He has cast away skeptical doubt; dwelling free from doubt, full of confidence in the good, he cleanses his heart from doubt.
"He has put aside these 5 hindrances, and come to know these paralysing defilements of the mind. And far from sensual impressions, far from unwholesome things, he enters into the first absorption, etc."
The overcoming of these 5 hindrances by the absorptions is, as already pointed out, a merely temporary suspension, called 'overcoming through repression' (vikkhambhana-paha^na). They disappear forever on entering the 4 supermundane paths (s. ariyapuggala), i.e. skeptical doubt on reaching Sota^panship; sensuous desire, ill-will and mental worry on reaching Ana^ga^miship; sloth, torpor and restlessness on reaching Arahatship.
For their origination and their overcoming, s. A. I, 2; VI, 21; S. XLVI, 51.
See The Five Mental Hindrances, by Nyanaponika Thera (WHEEL 26).