oracle applications architecture?

oracle applications is divided into 3 tiers
                                       1)desktop tier.
                                       2)application tier.
                                       3)database tier.

• Database tier contains RDBMS database called as oracle database server.

• Database tier stores all the data needed by oracle applications.

• Middle tier or Application Tier containing various servers configured with listeners like web server, forms server, admin server, reports server.

• Database server communicates with middle tier, doesn’t directly communicate with desktop tier.

• Desktop tier contains client desktop where users access oracle applications through web browsers.