An append query selects records from a table and then inserts them into another table. (Technically speaking, appending is the process of adding records to the end of a table.)
You may create an append query for a number of reasons, but usually you do it to transfer records from one table to another. You may want to use an append query to transfer records from one database to another. This technique is handy if you have duplicate tables in different databases (perhaps because different people need to use the database on different computers).
Once you’ve finished copying records to a new table, you may want to follow up with a delete query (Delete Queries) to remove the old versions.