This page uses OpenLayers to display Google maps. There's not much point in this, as if that's all you're going to do, you might as well use Google's API!
You can zoom in/out using the controls on the left, or pan the map by dragging it (hence 'slippy map'). If you double-click, it will zoom in and centre on the point clicked. You can also shift/drag to zoom into the highlighted area. You can if you wish resize the window. You can change the base layer by clicking on the '+' top right.
You can search for a lat/long coordinate by clicking on the search icon and entering the coordinate. This will create a marker and recentre the map at that coordinate. You can delete these markers by clicking the erase icon.
'Permalink' enables you to keep a particular view (coord/zoom level combination) for future reference, by storing it, adding it to your bookmarks, emailing it, etc.