While Tracker for ArcGIS is a released, supported product, right now it is limited to ArcGIS Enterprise users. Going forward, ArcGIS Online will be supported. Additionally, other mobile apps will display the tracks.
ArcGIS Online
The need for location tracking in ArcGIS isn't unique to ArcGIS Enterprise users. ArcGIS Online users also want the ability to access their mobile users' last known locations and use their location tracks to allocate resources and understand coverage in the field. Currently, this is planned for Q3 2019.
View tracks in other mobile apps
Mobile users can view their tracks in Tracker. However, Tracker is designed to run in the background. The ability to display tracks in other mobile apps on the same device—including Collector, Explorer, and Workforce, so that mobile users can see their tracks while using these other apps in their daily work—will be available soon.
The versions of Collector, Explorer, and Workforce that support viewing tracks weren't released when Tracker released. View the help for each app to determine its support and if there is a release available that displays tracks.