Use of OFFSET and LIMIT clause

I am getting 200000 records as a query output.
If I am calling the query by adding OFFSET and LIMIT clause.

select a.location, from buckethelp a order by a.location LIMIT 20000 OFFSET 20000

I need call the query 10 times to get 200000 records.

Which one of the above 2 operations, is more heavy for the server.

When OFFSET is given, then the query will process all the records and fetch only records given in OFFSET clause,
is that correct ?
Or if OFFSET is given then the query will process only records in OFFSET clause and return them.

WHEN OFFSET, LIMIT is given query needs to process OFFSET+LIMIT records and skip OFFSET records and produce LIMIT records.
If there is ORDER it needs to process all qualified records.

Check out

If you need to use OFFSET try 5.0