You download firmware that matches your specific hardware version. Installing the wrong version can cause device failure.
Some firmware versions allow for an online check. update+software+in+tplink+td854w+updated
Patches vulnerabilities that hackers could exploit. You download firmware that matches your specific hardware
Before starting, it is crucial to perform these safety checks to avoid "bricking" (permanently damaging) your router: How to update TP-Link Router Firmware for better security update+software+in+tplink+td854w+updated