How to use CSS Flexbox.

Flex is the css3 property. Flexible box or flexbox is complete control over the alignment, direction, order and size of our boxes. If you used

display:flex; 
justify-content: space-around;

The justify-content property also lets you distribute items equally inside a container.
Flex used alignment, direction, order and size.
Flex is dependend on three values maximum, minimum and fixed. Write flex property in css

flex: 0 0 0;
If you write flex: 10px 0 0; It means how much grow the iteam rest of the iteam.
If you write flex: 0 10px 0; It means how much shrink the iteam rest ot the iteam.
If you write flex: 0 0 10px; It means specifies the initial length of iteam.

If you used flex property in you webpae also you know about how flex is used and effect on webpage. Some of flex property you may used on webpage.

display: flex; to create a flex container.
justify-content to define the horizontal alignment of items.
align-items to define the vertical alignment of items.
flex-direction if you need columns instead of rows.
the row-reverse or column-reverse values to flip item order.
order to customize the order of individual elements.
align-self to vertically align individual items.
flex to create flexible boxes that can stretch and shrink.