RX/TX labeling standard
Given that you are talking about USB 3.0, this does use two additional pairs. These pairs are high speed 5Gbps differential pairs. One of them carries data from the host to the device, and the other carries data from the device to the host. These actually get crossed over, much like with RS232/UART - so the RX from one goes to the TX of the other and vice versa. If it is a device itself then these labels would be specific enough to understand. But it can cause confusion when building things from breakout boards where connectors are labelled with no device connected to indicate their reference direction (whose RX is it? ours or theirs!) - in that case you are better of referring to the correct specification or any documentation that came with the board.

The same is used in PCIe devices which have one or more simplex pairs for RX and the same number again for TX - so for example an 8 lane PCIe device actually has 16 pairs, 8 in each direction. Again here the RX and TX are crossed over. These are not always named RX and TX, you can also find them called HSI and HSO ('H'ighspeed 'S'erial 'I'n and HS 'O'ut). You also sometimes see the pairs labelled as +/- or P/N or just one (the inverting one) labelled 'n'.

When it comes to the other signals for USB, the D+/D- pair, these are actually bidirectional, so RX and TX make no sense. Instead you have the positive and negative (inverted) 'D'ata pins. Again here the +/- can be named P/N as well.

Firewire (IEEE1394) is similar to USB 2.0 lines in naming, you have a data pair and a strobe pair.



Usually you wouldn't have a pin labelled RX that transmits. I say usually because some UART type devices unhelpfully label the RX pin as TX and vice versa in which case you would connect RX to RX. But I've only ever seen one device which did that and to be honest it is a stupid thing to do!