I've been watching the skies for over 40 years and have learned a few things that will help you understand what you are seeing, for the most part.
Three major factors are in play when you see an artificiable object in the night sky: the positions of the object, sun and observer.
Other factors include the object's own motion, the path of its orbit, and the intrinsic nature of the object.
Most simply, a satellite will reflect sunlight to an earthly observer so long as it is exposed to sunlight and the observer remains in the path of the
reflection. Thus, the straight-line lights are merely satellites in sunlight moving across an area from which you can see the reflection. Here, size
matters, as the larger the reflective surface, the brighter the reflection.
The lights that brighten, fade out, and reappear are tumbling or rotating. At times, a reflective surface is sunlit, at others it is not. "Iridium
flares" are brilliant lights, sometimes visible in daylight, caused by satellites that are at other times completely invisible.
The reason that some of these observations appear to come in "waves" is due to the orbital path of the satellite and the rotation of the Earth. The
ISS is visible for days at a time from certain areas, then not at all as its path and the earth's rotation take you out of the field of view for the
Just as not everyone can witness a total solar eclipse, not everyone can see the same satellites at the same time, and some not at all. Like the
moon's shadow in an eclipse, the reflections will appear differently depending on the observers' relative locations to the object and each other.
The objects that appear to change course may be satellites that are maneuverable, or may be a coincidence of the appearance of one satellite as
another fades out of sunlight.
An excellent presentation in real time can be found at:"Live
Real Time Satellite Tracking"
The more familiar you become with the things are belong in the sky, the better able you will be to identify those that do not. An excellent site for
determining locations of planets, stars, satellites and other phenomena is "Heavens Above."
Taking a little time to learn will pay unlimited dividends in enjoyment and fascination. You may see some things nobody expected, too.