Some apps have dynamic content or change depending on your test data. Example: logging or registering to the app and then validating that the right email shows on the profile screen.
"Using Variables" you can choose any element on the screen/Object tree and assign a parameter to it (e.g the username in the Login screen)
Your parameter is then available throughout the rest of the test and will be set in runtime.
To assert a parameter choose "Assert Variable" and select the element you want to assert (e.g email address on the "Profile" screen).
Choose the type of element you are asserting: number or string
Decide on the logic. Options will vary depending on the type of element: number or string.
A list of available parameters you can choose from will appear.
Decide or you want to assert on a specific element or just look for the value anywhere in the page.
Once done choose "Add Action".