Mucus in the nose is a substance which provides moisturizing effect and cleans the nasal membranes. It also humidifies air, and halts the entry of the foreign particles at the level of nose. Normally nose and throat continually produce mucus which is swallowed, absorbed or spit out.
Post-nasal drip is a condition in which the individual has a feeling of accumulation of the secretion in the throat or sometimes even dripping of the secretions from the back of the nose. There are various responsible factors which are discussed in the flow of the matter.
This sensation can be caused by excessively thick secretions or by throat muscle and swallowing disorders.