The keyframes that do not have a orange line connecting them are the channels that are animated, all the others are 'held'.
This means that the is no change at all on every frame between frame 0 and 15 on the ones that are blocks of orange.
Technically they are animated - but there is no change in value, so they stay put (depending on constraints and parenting)
On the non orange ones, there is either a difference on the actual keyframes or on the in-between frames because of the animation curve handles.
You will need to look in the graph editor to see exactly what the curves are doing.