Type indicates whether a field contains characters (i.e., "char")
which contains any combination of letters or numbers, numbers (which
has a set number of decimal places), or integers (i.e., numbers
that range from 0 to 255 only).
Length shows the size of a field. Character fields have lengths that
are fixed, depending on their purpose. Description and note fields have
a length of 32000, which make them variable-length; their actual size depends
on how much data is entered into them.
Index indicates fields that are indexed in the database, which makes
them key fields for finding and sorting data. For best performances on
reporting and exporting, searches should made on index fields first.