Avalanche
Winning symbols are removed and replacements fall into the gaps, allowing the sequence to continue.
NetEnt's Gonzo's Quest uses an adventure setting and an Avalanche sequence in place of a simple one-stage display. Winning symbols disappear and new symbols fall into the gaps. That continuing sequence, its multiplier and the separate Free Fall feature explain the title more clearly than the theme alone.

Avalanche describes what happens after winning symbols are identified. Those symbols are removed, leaving spaces for new symbols to fall into. The new arrangement can produce another result within the ongoing sequence, rather than requiring a fresh ordinary spin.
A multiplier can increase during consecutive successful Avalanches and resets under the game's stated conditions. Its value therefore belongs to a particular stage of the sequence. Seeing a multiplier label does not by itself say that any next arrangement will qualify.
Free Fall is a separate feature reached through its qualifying symbols and rules. Distinguish the ordinary round, continuing Avalanches and this feature stage before trying to follow an example. The game's own information controls exact values and conditions for the version in question.
Winning symbols are removed and replacements fall into the gaps, allowing the sequence to continue.
Consecutive qualifying stages can change the multiplier, which resets under specified conditions.
A separate triggered feature with its own conditions, rather than another name for every falling-symbol sequence.

Imagine an initial qualifying arrangement followed by falling replacements that also qualify. Those are successive stages of the same Avalanche sequence. If the next arrangement does not qualify, the continuation ends under the rules rather than guaranteeing another successful stage.
The adventure artwork provides recognition, while the sequence explains function. Read a multiplier in relation to its current stage and the reset condition. Keeping those details together prevents an isolated high value from becoming a misleading expectation.
NetEnt. This collection also explains its differently structured Starburst title.
Winning symbols are removed and new symbols fall into their places, potentially continuing the sequence.
No. Free Fall is a separately triggered feature, while Avalanche describes the falling-symbol mechanism.
No. A multiplier rule applies to qualifying outcomes; it does not guarantee that the next stage will qualify.