What Can Downloaded linux Image Do that linux Onboard Can't

What is advantage to install the image update. The Beaglebone Black has 2 GB memory, but the downloaded image size is 3.9+ GB. How can this be installed. What have I missed.
Thank you

The image creates an installer onto the SD card that when runs, installs the image on the 2GB eMMC.


What image did you download and from where ?