So a bus that is being driven that has the outer ring plus a single Led in the centre this would be the daytime running lights or drl with sidelights, and the sidelights on would just show the single Led?The sidelight is a single LED in the centre which isn't especially visible on its own. The indicator is most of the rest of the unit with the DRL being a 1 LED wide ring around the outer edge.
Rear lights depend on what they've been specced with, but generally the upper light is the tail, brake and indicator while the lower is either combined fog and reverse or one of each on their respective sides.