According to TOI Google has started a new feature to the users of
YouTube Android and iOS app in India, Indonesia and the Philippines. The
feature allows users to temporarily store videos offline to watch later
during short periods of low or no internet connectivity.
According
to Google, videos can be played back without an internet connection for
48 hours once taken offline. it adds that a large part of popular
YouTube content in India is already available for users to view offline,
including video content from labels like T-Series, Saregama and Yashraj
Films. 
To download videos on YouTube just click on the offline icon. Content owners can choose if they want to opt to allow offline viewing for their media. A YouTube spokesperson had previously informed TOI(Time of India) that views of the videos and ads will be tracked offline as well.
The move is aimed at increasing the use of YouTube as offline viewing
will allow users to download and store more content when they get access
to a good internet connection, and view it at a later time. It will
also improve the viewing experience eliminating buffering due to bad or
intermittent connectivity.