This classic layout type has been around since switches were first made for electric trains. It is basically an altered oval. Four standard switches make passing sidings at either end of the layout, while a fifth switch makes a long siding. That siding can also be a link for an extension to the layout
A more complex version uses three standard switches to make an inner oval with sidings inside. #4 or #6 switches can be used to make more sidings at the bottom. Simple layouts of this type remain popular for various reasons. They are great by themselves, and can be good bases from which to expand.