If an element has flex: 1, this means the size of all of the other elements
will have the same width as their content, but the element with flex:
1 will have the remaining full space given to it
This applies if the parent element has
display: flex;
The default values are set to 1 1 0% (which are the shorthand values for flex-grow flex-shrink flex-basis respectively) probably because these are the values that make the most sense for "flex" items. Here are what exactly those values mean: