In MCPE/Bedrock, the commands sort of appear as you type them, giving you options to choose from. I typed in
/testfor @p[r=3, and then, these appeared:
What do all these different values mean? I know about
Name, so you don't need to list those when answering this question.
Also, slightly off-topic but I am looking to create a testfor command that activates a comparator when there is a player with a certain item in their hand. Is there one of these tags that would help me do this?