Progress and activity indicators are visual indications of an app loading content. A progress indicator should be used to represent a single type of operation the app does - if you have two operations being done then you need to use two indicators.
Progress indicators
Guidelines
In Material Design are two types of progress indicators - determinate and indeterminate. A determinate indicator displays how long an operation will take and is best used when that time is detectable. An indeterminate indicator just displays an unspecified wait time, used when you want to signify that the app is working on a task.
More information
Find out more about progress indicator types and when to used them on the dedicated Material Design Guidelines Page.