SubDatasheet is a misleading name. a subdatasheet is not a subcategory of
records in a single table; it is simply a way to see related records *from
another table*, in the first table's datasheet view.

an Access table looks similar to an Excel spreadsheet (rows and columns),
but it is very different. the "rows" are records, and the "columns" are
fields. (there are no "cells" in an Access table.) if your data originated
in an Excel file, it is very probably not normalized - not correctly grouped
by relationships. if you're just doing something "quick and dirty", for
yourself, to analyze and/or manipulate the data, you may not need to bother
setting up the tables and relationships correctly. BUT if you're building a
database that is going to accumulate data (either via Excel or by manual
data entry), and be used over and over, and especially if other people are
going to use the database, i strongly recommend that you invest the time in
learning the basics of both the software and the concepts of relational
database design (often referred to as data modeling, or table
normalization). there are numerous good books on the market, including

Microsoft Access <version> Bible by Prague and Irwin
(teaches you how to use the software effectively)
Database Design for Mere Mortals by Michael Hernandez
(teaches you data modeling)

and many websites that offer information and tips. here are a few that will
help you start out on the right foot.

http://www.mvps.org/access/tencommandments.htm
(as a newbie, pay special attention to #s 1, 2, 3, 7, 8 and 10.)
http://www.mvps.org/access/lookupfields.htm
http://www.mvps.org/access/general/gen0012.htm

hth