What's the Patch Function in PowerApps?
In PowerApps, the Patch function is used to generate a record in the data source or to edit single or several records without impacting other attributes. 
Using Patch function, You can do the following:
- Use Patch with the Defaults function to create records.
 
- Modify one or more records of a data source.
 
- Update the records in a data source without affecting other properties.
 
- Perform the updates that require no user interaction.
 
- Use the ForAll function to update or create multiple records using the Patch function
 

For more details check this article Power Apps Patch function