COMMENT
With FargoRating they try to clarify that as far as they are concerned, if you have less than 200 games in then you don't have a rating. You should treat it that way too.
DETAIL
FargoRate = 200 games
Starter Rating = Something someone made up and put in the system
Preliminary Rating = A blend of your starter rating and your initial results while under 200 games.
Rating can change based on what the system knows about you, about the players you've played, the players they've played, and so forth. Fargo Ratings can change due to that, but only in minor increments. Preliminary Ratings can change wildly...it's one of the reason they don't consider Preliminary Ratings to be actual ratings and it's an incentive for you to get actual games into the system.
It's worth knowing how a starter rating works. When you have zero games in the system, it treats it like you have 200 fake games where you performed at that starter rating level. When you have 50 real games in the system, it treats it like you have 50 real games at your actual performance level + 150 fake games in the system at your starter rating level. When you have 200 real games in the system, it treats it like you have 200 real games at your actual performance level + 0 fake games in the system at your starter rating level.
So the first thing to be aware of is that league operators and tournament directors can change your starter rating. And that change can cause the wildest shifts in your rating. Another thing that can cause wild shifts is not because your opponents got better, so much as it learned more about your opponents. If you're in a region that had very little games in the system then but today have a lot more games loaded, it'll see not just your ratings shift a lot but it will cause your rating to shift too. Not because it thinks people got better...but because it today knows more about those players.
Let's be honest, most players don't improve by significant amounts over time. Most players stay the same skill level over decades...and then a handful of players skyrocket up major jumps in skill over very short periods of time because they drastically changed their habits in terms of practice and competition. Most people don't change their habits.