Periodization is any planned variation in training stress. So the answer to your first several questions is "yes".
So, it's a pretty broad topic. Some people have given names to different methods, but often the names are confusing, and people sometimes use the same name for different approaches.
Something as simple as alternating light days/heavy days is periodization.
A popular approach is to do cycles of different emphasis, like Lou Schuler's books suggest--several weeks of strength emphasis, followed by endurance or hypertrophy, etc.
Matt Zito uses an interesting approach which I haven't seen suggested elsewhere. He has 4 workouts but lifts on a MWF schedule, so workout A comes up on Monday, then the next week workout D is on Monday, and so on. Monday is always his heavy day, Wednesday light and Friday medium (as I recall). That way, the main lift of each of the 4 workouts comes up for heavy lifting once in 4 weeks.
Some will just cycle the rep-set scheme, maybe lifting 4x3 for 4 weeks, then switching to 3x12 for 4 weeks.
I have used this for some lifts: In one cycle I'll lift 6-10 singles at 90% of 1RM or of a recent relative max. Next cycle 5-7 doubles at the same weight, then next cycle 4-5 triples at the same weight, then 4th cycle either a deload or just add 5 or 10 pounds and repeat the pattern.
Our greatest fear should not be of failure, but of succeeding at things in life that don't really matter.--Francis Chan