What do the 2 triangles beside the WiFi icon mean? I'm running Oreo 8.1.0 on a Xiaomi A1. In the status bar, I see the following three similar icons beside the WiFi icon, never more than one of them at a time:

One of them is a solid equilateral triangle, with a vertex at the top, occupying the top half of the status bar.

One is a solid equilateral triangle, with a vertex at the bottom, occupying the bottom half of the status bar.

And the third is the combination of the other two.



I can't find any info about all of them by searching online, nor at Material Design's Icons.
What do they mean?
I guess you think on up/down arrows next to the WiFi signal indicator. They are called network activity arrows/indicators.
Those arrows are showing when there is network activity. Arrow pointing up means you are uploading data (doesn't necessarily mean that you are uploading a file but rather that there is network activity, when you search something on Google you need to send data first - request to be able to receive) and an arrow pointing down means that phone is receiving data via the internet. They can appear separately or both at the same time.
They also appear next to cellular signal strength if cellular data is active. Sometimes arrows are inside of WiFi/cellular icon, it really depends on the device manufacturer.