i. flex-grow
This defines the ability for a flex item to grow if necessary. It dictates what amount of the available space inside the flex container the item should take up.
ii. flex-shrink
This defines the ability for a flex item to shrink if necessary. It dictates what amount of the available space inside the flex container the item should take up.
iii. flex-basis
This defines the default size of an element before the remaining space is distributed. It can be a length (e.g. 20%, 5rem, etc.) or a keyword. The auto keyword means "look at my width or height property".