Simple! Using OPAL/Miner, you can download table DD02T. This table contains a list of every SAP table and it's description. Alternatively, you can download table DD02L which contains some of the table attributes if that is what you are after. You can also download both and join them to produce a more comprehensive list of tables, attributes, and their descriptions. Be warned that in SAP release 4.6C the list consists of roughly 90,000 table names.