The entities matching the target query
A target selector is made up of 3 parts:
First there's the @ (at symbol) part,
notifying us that this is in fact a target selector
Secondly there's the target selector type (a, e, p, r, s),
this specifies what kind of entities we should query for
and in what way.
Thirdly there's the arguments, they are split up in a comma-separated list in the argument=value format.
This results in an input similar to:
@e[type=player,gamemode=creative,limit=3]
Parse target selector argument.