One of the most important things to consider when creating and using a database is how to organize the data. The layout should be decided when you first establish the database. The layout can be decided on or changed at a later date, but this is almost guaranteed to be a tedious, if not difficult, task. If it is never decided on, a database will become disorganized over time and introduce significant hurdles when upgrading components or running backups.
By default, a new PostgreSQL database has only one schema - namely, public. Most users place all the data (their own and third-party modules, such as PostGIS) in the public schema. Doing so mixes different information from various origins. An easy method with which to separate the information is by using schemas. This enables us to use one schema for our data and a separate schema for everything else.