For writing Appium tests you require:
Driver Client: Appium drives mobile applications as though it were a user. Using a client library you write your Appium tests which wrap your test steps and sends them to the Appium server over HTTP.
Appium Session: You have to first initialize a session, as such Appium test takes place in that session. Once the Automation is done for one session, it can be ended.
Desired Capabilities: To initialize an Appium session you need to define certain parameters known as “desired capabilities” like PlatformName, PlatformVersion, Device Name and so on. It specifies the kind of automation one requires from the Appium server.
Driver Commands: You can write your test steps using a large and expressive vocabulary of commands.
