When you run the code, below sequence of events happens.
Command to create a new session is sent to Appium server at http://0.0.0.0:4723/wd/hub
Appium looks at the requested capabilities and decides which automation library should be
called to run the tests.
If platformName capability is iOS, then XCUITest will be used to automate iOS apps.
If it is android, Android SDK will be used to automate android apps.
Applications can be mainly of 2 types - native and web. If web application needs to be automated,
carthage will be used to automate the browser in iOS devices.
For native apps, carthage is not required. On android apps, Google’s UIAutomator will be used.
Below image shows how appium architecture looks like. The client talks to Appium HTTP server.
Appium server reads the capabilities sent by the client and tries to create a new session using one
of the automation server. For example - if the automation name capability is UiAutomator2,
appium will send a request to the UiAutomator2 server. if platformName capability is Windows, request
will be sent to winappdriver server and so on.