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What is command context?

• Defaults
• Context in Functions

All commands exist in a context.

This context is first set when the command is run and consists of multiple parts that all describe the “situation” that a command is run in.

• the execution position (x / y / z and dimension)
• the executing entity
• the execution rotation
• (the anchor)

All of which can be modified individually with the 1.13+ Java as well as 1.19.1+ Bedrock execute command.

See the Minecraft wiki on the execute command for which subcommands modify which context.

Defaults

When a command is run, it will get some default values depending on how it is run.

• A command run from chat is executed as and at (so positioned and rotated as) the player who runs it.
• A command run from a commandblock is executed with the position set to the center of the commandblock in all three axes. It is always rotated 0 0, so facing straight forward in south (positive z) direction. There is no executing entity.
• A command run from a function can have various values, as functions themselves keep context. See below.
  • A scheduled command does not keep context
  • Tick and load functions run at world spawn
• A command run from the server console is executed at world spawn.
• A command run from an NPC ^{[Bedrock Edition Only]} is run as and at the NPC

Context in Functions

Functions keep the context that they’re run in.

So a function run in chat will have the same defaults as any other command run from a player in chat. The same is true for a function command run from a commandblock, it will have the same context as any command run from a commandblock would.

A command run from either the #minecraft:load or #minecraft:tick function tags will run positioned at world spawn (at the lowest end of the block, unlike the commandblock), rotated 0 0 and without an executing entity.

This allows a lot of optimization since you can use a selector once, running the function as that entity and then refer to that entity as @s for the rest of the function. It also allows for entityless raycasting as the position and rotation are preserved between function calls.

You can find a more in depth explanation on The Minecraft Wiki