CSS display property && flex

 https://www.w3schools.com/cssref/pr_class_display.asp

https://www.w3schools.com/cssref/css3_pr_flex.asp

Flex:

The flex property sets the flexible length on flexible items.

Note: If the element is not a flexible item, the flex property has no effect.

Example

Let all the flexible items be the same length, regardless of its content:

#main div {
  -ms-flex: 1; /* IE 10 */
  flex: 1;
}

inline	Displays an element as an inline element (like <span>). Any height and width properties will have no effect	Demo ❯
block	Displays an element as a block element (like <p>). It starts on a new line, and takes up the whole width	Demo ❯
contents	Makes the container disappear, making the child elements children of the element the next level up in the DOM
flex	Displays an element as a block-level flex container
grid	Displays an element as a block-level grid container
inline-block	Displays an element as an inline-level block container. The element itself is formatted as an inline element, but you can apply height and width values
inline-flex	Displays an element as an inline-level flex container
inline-grid	Displays an element as an inline-level grid container
inline-table	The element is displayed as an inline-level table
list-item	Let the element behave like a <li> element	Demo ❯
run-in	Displays an element as either block or inline, depending on context
table	Let the element behave like a <table> element
table-caption	Let the element behave like a <caption> element
table-column-group	Let the element behave like a <colgroup> element
table-header-group	Let the element behave like a <thead> element
table-footer-group	Let the element behave like a <tfoot> element
table-row-group	Let the element behave like a <tbody> element
table-cell	Let the element behave like a <td> element
table-column	Let the element behave like a <col> element
table-row	Let the element behave like a <tr> element
none	The element is completely removed
initial	Sets this property to its default value. Read about initial
inherit	Inherits this property from its parent element. Read about inherit