Layer Group

click on the icon in the upper right hand corner of the map to select different maps.

Also a demo of Popup Overlay. The popups are created using Popovers from Bootstrap.

Click on the map to get a popup. The popup is composed of a few basic elements: a container, a close button, and a place for the content. To anchor the popup to the map, an ol/Overlay is created with the popup container. A listener is registered for the map's click event to display the popup, and another listener is set as the click handler for the close button to hide the popup.