Asceticism (Greek: askēsis) is a word that describes a certain way of living. In this kind of life, a person gets rid of worldly pleasures for religion or spirituality. A person might not have sex or drink alcohol. One might spend much of their time in prayer or meditation. Often, the reason is to follow goals of Christianity and the Indian religions (including yoga). These teach that salvation and freedom involve a process of changing one's mind and body. This is done by limiting speech, what one thinks and does with the body.
The earliest people who practiced Buddhism, Jainism, and the Christian hermits, lived very simply and without luxury. They rejected sensual pleasures and keeping money. This did not mean that life could not be enjoyed. But spiritual and religious goals are hindered by such indulgence.