The structure of the query

Let's take a look at the query line by line to understand what it's about.
#Cats
Anything starting with # is a comment in SPARQL that the query service will ignore.
SELECT ?item ?itemLabel
A query "selects" something based on certain rules specified in the query.
In this case, it's a variable we've chosen to name ?item
. The ?
indicates
that this is a variable. The name is just something you pick for convenience.
In this case, since we're looking for items, calling the variable ?item
makes
sense, and makes it easier for other people to interpret your query (or for
you to interpret it when you come back later and have forgotten why you did
what you did).
?itemLabel
is a special kind of variable. It applies a modifier,
or a Label
, to the variable.