Explain how flexbox works in CSS

Flexbox, formally known as the Flexible Box Layout Module, is a one-dimensional layout model in CSS that offers a more efficient way to align and distribute space among items in a container, even when their size is unknown or dynamic. The main idea behind flexbox is to give the container the ability to alter its items' width/height (and order) to best fill the available space (mostly to accommodate to all kinds of display devices and screen sizes). A flex container expands items to fill available free space or shrinks them to prevent overflow.

Basic Concepts of Flexbox:

1. 1. Flex Container: The element on which you apply `display: flex` or `display: inline-flex` becomes a flex container, and its children automatically become flex items.
2. 2. Flex Items: Direct children of the flex container.
3. 3. Main Axis and Cross Axis:
4. - The main axis is defined by the `flex-direction` property and can be either horizontal (`row`) or vertical (`column`). It's the primary axis along which flex items are laid out.
5. - The cross axis is perpendicular to the main axis and its direction depends on the direction of the main axis.

Properties of the Flex Container:

1. - `display`: This defines a flex container. Use `display: flex;` for a block-level flex container or `display: inline-flex;` for an inline flex container.
2. - `flex-direction`: This establishes the main axis, thus defining the direction flex items are placed in the flex container. It can be `row`, `row-reverse`, `column`, or `column-reverse`.
3. - `flex-wrap`: By default, flex items will all try to fit onto one line. You can change that and allow the items to wrap onto multiple lines, with `wrap` or `wrap-reverse`.
4. - `justify-content`: This defines the alignment along the main axis and helps distribute extra free space. It can be `flex-start`, `flex-end`, `center`, `space-between`, `space-around`, or `space-evenly`.
5. - `align-items`: This defines the default behavior for how flex items are laid out along the cross axis. It can be `stretch`, `center`, `flex-start`, `flex-end`, or `baseline`.
6. - `align-content`: This aligns a flex container's lines within when there is extra space on the cross-axis. Similar values to `justify-content` and it's used when there is more than one line of flex items.

Properties of the Flex Items:

1. - `flex-grow`: This defines the ability for a flex item to grow if necessary. It accepts a unitless value that serves as a proportion.
2. - `flex-shrink`: This defines the ability for a flex item to shrink if necessary.
3. - `flex-basis`: This defines the default size of an element before the remaining space is distributed.
4. - `flex`: This is a shorthand for `flex-grow`, `flex-shrink`, and `flex-basis` combined.
5. - `align-self`: This allows the default alignment (or the one specified by `align-items`) to be overridden for individual flex items.

Flexbox layout is most appropriate to the components of an application and small-scale layouts, while the Grid layout is intended for larger scale layouts. Flexbox makes it simple to design flexible and efficient layouts without having to use float or positioning hacks.