A snapshot is a frozen image of the DB instance's storage volume. It helps to restore a database to a particular point in time. Usually, point-in-time recovery is performed when a database is corrupted or by mistake some data has been dropped (that is, deleted), to bring a database back to the last healthy state. At the time of creating an Amazon RDS instance, a daily snapshot schedule has already been configured, but it may sometimes be required to take a manual snapshot of the DB instance before performing any maintenance tasks on the database. A snapshot will back up an entire DB instance including all databases, tables, and other resources existing on it.
Creating a snapshot for a multi-AZ DB instance doesn't bring many performance implications, but taking a snapshot for a single-AZ DB instance may suspend DB I/O, for a few seconds to minutes...
