Physical thirst; the need or desire to drink. Often used in expressions like 渇きを癒す (to quench one's thirst).
I felt thirsty.
I quenched my thirst with cold water.
Metaphorical thirst or hunger for something abstract, such as love, knowledge, power, or success. Often used with ～への渇き.
He has a strong thirst for knowledge.
A hunger for success drove him.
I quenched my thirst with cold water.
After the long meeting, I felt thirsty.
He had a thirst for knowledge.
The book satisfied the thirst in his heart.