Anybody can explain what is align item in css3

Answer 1

Align helps format your content to the left, middle, or right side of the page, and there are bonus options like fixed, etc.

Answer 2

'align-items' is a flexbox related css property ('display:flex' should be set at target element on wich you want to apply it).
According to the flex element direction, it defines the alignment style of its content.

https://css-tricks.com/almanac/properties/a/align-items/
https://css-tricks.com/snippets/css/a-guide-to-flexbox/

Answer 3

Thanks Anthony and visph