Stride Length is the distance you cover with each step.
Measured from toe-off to footstrike, Stride Length is rather self-explanatory. It can be useful to gauge your running efficiency — especially when compared with Vertical Oscillation, Cadence, and other workout metrics.
In order to monitor and record Stride Length, you can wear a Garmin Running Dynamics capable Forerunner-series watch (such as the 935), and an additional sensor (the HRM-RUN or HRM-TRI chest straps, or the RD Pod). Another option is to use the Stryd footpod with a compatible watch from Suunto, Polar, etc.
Find it in SportTracks
If you use the required hardware, you can find Stride Length in your Workout Detail charts: