Method of spiritual practice. Upasanas can be for gaining some worldly objectives called as Kamitartha Upasana or they can be Nishkam Upasana, which meansthat the practice is for no worldly objective and is done as a matter of duty.
Uapasana in Sanskrit literally means "Sitting near" but normally the term is used in Hinduism to denote a prescribed method for approaching a Deity/God or getting close to deity. In Vedas some Upasanas are prescribed where one meditates on all pervading Brahman as some aspect of creation such as fire, water, directions, food, mind etc. In other words, Upasana can be described as a systematic practice of a prescribed method of worship for pleasing and winning the attention of the deity or it can be a deity less practice of austerities meditating upon some aspect of nature as told in some Vedic Upasanas.