Terms like moveLast, BOF, EOF are for dealing with a text file or a database.
In this case you are using object oriented programming  and therefore you use
an object (e.g. a spreadsheet) which may be in a collection (Spreadsheets) a
collection has a count (How many spreadsheets are there) and each item in the
collection can be referred to by its index (1 to Count) or by its name.