To understand what location SDKs are, we need to first clarify what an SDK is.
An SDK stands for a software development kit. They are codes that an app developer puts into their application. It can be understood as a toolkit that app developers and publishers add to their existing app to provide new functionalities, such as location tracking.
Location SDKs use the location functionalities within an operating system, like the GPS of iOS & Android, and additional location-related data to provide improved accuracy and insight into the user's behavior. The way a location SDK operates will differ between kits. Some will only operate when the app is open, while others will run in the background and collect location data and other relevant information from the device. In general, for the location SDK to operate it will need the user's permission.