Minecraft wiki entry for scoreboard, associated text: Syntax
scoreboard players reset <targets> [<objective>] (Java Edition)
scoreboard players reset <player: target> [objective: string] (Bedrock Edition)
Description
Deletes score or all scores for the targets. If <objective> is specified, then only that objective is cleared. Otherwise, this applies to all objectives.
Note that this does not merely set the scores to 0: it removes the targets from the scoreboard system (or for the given objective) altogether.
In Java Edition, this will also disable the target players' ability to use /trigger command (on the given objective if specified).
Arguments
JE: <targets>: score_holder
BE: player: target: WildcardCommandSelector<Actor>
Specifies the score holders.
Must be a selection of score holders. It may be either a target selector, a player name, a UUID‌[Java Edition only], a unique ID of an entity‌[Bedrock Edition only], or * for all score holders tracked by the scoreboard. Named player needn't be online, and it even needn't be a real player's name.
JE: <objective>: objective
BE: objective: string: basic_string
Specifies the objective.
In Java Edition, it must be an valid scoreboard objective name. In Bedrock Edition, it must be either a single word that isn't a number (allowed characters: -, :, ., _, A-Z, a-z, and 0-9) or a double-quoted string.
Result
Command Trigger Java Edition Bedrock Edition
... reset ... the arguments are not specified correctly Unparseable Failed
<targets> or player: target fails to resolve to one or more score holders Failed
... reset ... [<objective>]
... reset ... [<objective: string>] the objective doesn't exist
... reset <player: target> all the targets are not tracked by any objective N/A
... reset <player: target> [<objective: string>] all the targets are not tracked by the specified objective
any On success Reset the score(s).
Output
Command Edition Situation Success Count /execute store success ... /execute store result ...
... reset ... Java Edition On fail 0 0 0
On success 1 1 the number of the targets
Bedrock Edition On fail 0 N/A N/A
On success the number of the targets that is tracked by the scoreboard (or the specified objective) N/A N/A