What is RX and TX?

In plain language

RX means receiver: the input, where the signal comes in from a player, console or PC. TX means transmitter: the output, where the signal goes on to a display, projector or AV receiver.

Status readouts use the pair constantly. RX: connected means a source is present at the input. TX: connected means a sink is present at the output. If only one of them says connected, you already know which half of the chain to look at.

Why it matters in your setup

EDID readouts split the same way, and this is where people get turned around. EDID TX is what the connected display advertises. EDID RX is what the source is actually being told. On a device that only passes EDID through, the two are identical. The moment they differ, something in the middle is rewriting the negotiation — which is either the fault, or the fix.

What the DR HDMI 8K does with it

The DR HDMI 8K reports RX and TX state on the OLED and in the browser, and it shows both EDID sets side by side: names, video formats, video caps, and Dolby, DTS and PCM audio for each. Comparing the two lines is the quickest read on what the unit is changing.