Cascading, Avalanche, Sweeping, Swooping, Tumbling, Collapsing, Rolling, Falling reels are exactly identical in terms of their meaning. I guess different software providers call this feature differently because of possible copyright issues, causing some confusion among slot players along the way.
Cascading reels (I will stick to this name throughout the article) means that if you have managed to hit some win per payline, then involved paying symbols are going to disappear (often being accompanied by vivid animation). New symbols are going to replace them falling from the top (that’s why this feature is called the way it is). These new fallen symbols might or might not form a new winning per line. This is the whole point of having the cascading reels feature from the players’ perspective.
If newly cascaded symbols produce a new win per line, then they are going to disappear as well. Their place will be taken by a new batch of cascading reels. This is going to continue until there is no win per line hit.
As you have figured out, Cascading reels may transform even small winning into something much bigger.