Why do skaters who aren't jammers sometimes line up behind the Jammer line?

It is a minor penalty for any skater other than the jammers to line up behind the Jammer line. In order to intentionally draw a fourth minor (and subsequent trip to the penalty box) at the most strategically advantageous time, skaters will sometimes line up behind the Jammer line. This is sometimes called "poodling" (or "pug" or "cougar").

Why are all those skaters taking a knee before the first whistle?

If an entire team is on their knees, the result is a no pack situation. Because there is no pack, the second whistle (releasing the Jammer) will happen right away. Speeding up the Jammer whistle maximizes the amount of time the Jammer(s) can score points. Teams will often take a knee if the other team's Jammer is in the box, when the other team is playing short with Blockers in the box, or when they are losing and need as much time as possible to score points in order even the score.

Why is that team trapping an opposing skater and going SO SLOW while the opposing Jammer is in the box?

When the opposing Jammer is in the box, a team might trap a member of the jammerless team behind them in order to define where the pack is. If the pack is moving slowly (or not moving at all), it is easier for their unopposed Jammer to catch up to the pack on the track, allowing her to make more passes and score more points.

Why is that skater standing up in the penalty box?

While serving a penalty, a skater is required to stand for the last 10 seconds (but must remain seated until then).

That skater just stepped outside the track, why didn't she get a penalty?

If an action has no impact on game play (say, she stepped outside the track far away from any other skater and then just stepped back in), no penalty is called. As long as the skater does not exit the track in order to avoid a hit, and as long as she does not better her position in relation to another skater when re-entering the track, it is legal.

What are all those hand signals that the referees are doing?

Because of the noise and organized chaos going on, a series of hand signals have been developed to aid in communication.

What are those people with whiteboards scurrying around doing?

In addition to the skating referees wearing stripes, there are also a host of non-skating officials (NSOs) that keep track of scoring, penalties, and time spent in the penalty box.

She was the first skater through the pack, why isn't she the Lead Jammer?

If a skater doesn't pass all pack skaters legally and in-bounds, she is not eligible for Lead Jammer status. It is possible, however, for her to regain her eligibility for Lead Jammer status by re-entering the pack and re-passing those skaters legally and in-bounds.