What are jet streams? How do they affect the climate?

Jet streams are fast flowing winds moving in the upper air of the atmosphere.
(i) Sub-tropical Westerly Jet Streams: These jet streams are located
approximately over 27′-30′ north latitude; therefore, they are known
as sub-tropical westerly jet streams. over India, these jet streams blow
south of the Himalayas all through the year except in summer. During
winters, the cyclonic disturbances are brought into India by these jet
streams.
(ii) Tropical-easterly Jet Streams: These easterly jet streams blow over
peninsular India, approximately over l4’N, during the summer months.
it is believed to be responsible for the sudden outbreak of the south-west
monsoon in India.