What is Beacon refer to?

Ground Control Software Mission Planner
1

what is Beacon of Param .EK3_SRC2_POSXY ?

2

https://ardupilot.org/copter/docs/common-nooploop.html or https://ardupilot.org/copter/docs/common-marvelmind.html

3

Thank you so much,Eosbandi!