In brief
align-self lets an individual item differ from the shared align-items setting. It suits a card or icon needing its own alignment.
Useful to know
align-self lets an individual item differ from the shared align-items setting. It suits a card or icon needing its own alignment. [1]
Apply it to the item rather than as a common setting for all neighbours. In flex, remember the cross axis; this is not a command for arbitrary movement in every direction.
Sources
For further detail and to check the information: