Android Interface Definition Language is a special language that allows a server and a client to establish interface for Inter Process Communication (IPC).
AIDL - is a special language that allows a client and a server process to establish interface that can be used for Inter Process Communication. This interface is defined in the .aidl files. The syntax of the Android interface is similar to the syntax of Java interfaces but has several peculiarities. Aidl files are compiled into the Java files by a special aidl tool.
By default, for security reasons all applications in Android run with their own uid and in different processes. At the same time, so as Android is a mobile operating system it should provide abilities to maximize the reuse of components of the applications. Thus, the mechanisms for exchanging information have to be implemented. These mechanisms are called Inter Process Communication. For Android there was implemented a special IPC mechanism called Binder.
To communicate with each other Android process have to decompose the information into primitives that can be understood by Binder driver. This driver have to send these primitives to remote process and compose them there into the sent information. The process of decomposing and composing is difficult to write. Thus, OHA has proposed a special tool called aidl to facilitate this process.
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