display

This defines a flex container; inline or block depending on the given value. It enables a flex context for all its direct children.

.container {
      display: flex; /* or inline-flex */
    }

Note that CSS columns have no effect on a flex container.

flex-direction

This establishes the main-axis, thus defining the direction flex items are placed in the flex container. Flexbox is (aside from optional wrapping) a single-direction layout concept. Think of flex items as primarily laying out either in horizontal rows or vertical columns.

.container {
      flex-direction: row | row-reverse | column | column-reverse;
    }

• row (default): left to right in ltr; right to left in rtl
• row-reverse: right to left in ltr; left to right in rtl
• column: same as row but top to bottom
• column-reverse: same as row-reverse but bottom to top

flex-wrap

By default, flex items will all try to fit onto one line. You can change that and allow the items to wrap as needed with this property.

.container {
      flex-wrap: nowrap | wrap | wrap-reverse;
    }

• nowrap (default): all flex items will be on one line
• wrap: flex items will wrap onto multiple lines, from top to bottom.
• wrap-reverse: flex items will wrap onto multiple lines from bottom to top.

flex-flow(applies to: parent flex container element)

This is a shorthand flex-direction and flex-wrap properties, which together define the flex container's main and cross axes. Default is row nowrap.

      flex-flow: <'flex-direction'> || <'flex-wrap'>

Note that CSS columns have no effect on a flex container.

justify-content

This defines the alignment along the main axis. It helps distribute extra free space left over when either all the flex items on a line are inflexible, or are flexible but have reached their maximum size. It also exerts some control over the alignment of items when they overflow the line.

.container {
      justify-content: flex-start | flex-end | center | space-between | space-around | space-evenly;
    }

• flex-start (default): items are packed toward the start line
• flex-end: items are packed toward to end line
• center: items are centered along the line
• space-between: items are evenly distributed in the line; first item is on the start line, last item on the end line
• space-around: items are evenly distributed in the line with equal space around them. Note that visually the spaces aren't equal, since all the items have equal space on both sides. The first item will have one unit of space against the container edge, but two units of space between the next item because that next item has its own spacing that applies.
• space-evenly: items are distributed so that the spacing between any two items (and the space to the edges) is equal.