<flex> CSS typeThe <flex> CSS data type denotes a flexible length within a grid container. It is used in grid-template-columns, grid-template-rows and other related properties.
The <flex> data type is specified as a <number> followed by the unit fr. The fr unit represents a fraction of the leftover space in the grid container. As with all CSS dimensions, there is no space between the unit and the number.
1fr /* Using an integer value */ 2.5fr /* Using a float value */
.grid {
display: grid;
grid-template-columns: 1fr 1fr 2.5fr 1.5fr;
}