What the lookup tells you
The country comes from the calling code, the place from the area code, and the operator from the mobile prefix. The length check tells you whether a number of that length can exist in that country, which catches a missing or extra digit.
Why the operator may differ
Most countries let subscribers keep their number when they switch operator. The prefix only says who the range was originally assigned to; the current operator is known only to that country’s porting database.
Your number stays on your device
The lookup runs in your browser. Only the prefix table for the relevant country is downloaded.