What is main axis size Flutter?

MainAxisSize.min says, squeeze the rows together and leave unused space (100) at the end (or beginning or both ends depending on alignment)

Using mainAxisAlignment in a Row lets you align the row’s children horizontally (e.g. left, right). The cross axis to a Row ‘s main axis is vertical. So using crossAxisAlignment in a Row lets you define, how its children are aligned vertically . In a Column , it’s the opposite.19 Ara 2018

MainAxisAlignment is a property of Column widget. It is used to arrange children widgets into vertically format according to given axis . Today we would use the Column widget and make children widget into single column format in flutter.