This one's pretty simple.
It's a SFP module, but it has an RJ-45 plug instead of a glorious fiber cable. It does gigabit, which is pretty good.
The PHY is a Marvell 88E1111, this surprisingly has a public datasheet. It can take in SGMII (or basically 1000Base-X but electrical), and convert it to standard 1000Base-T. It apparently also does triple-speed, not sure how the host device will handle that.
Probably the most interesting thing about it is the magnetics, it's hard to see but if you look above it looks like the magjack is a custom part with a flex PCB soldered to the SFP carrier board. Alternately, it might just be shielding.
The bottom has a 25 MHz clock, and a couple of mystery ICs. The SSOPs near the edge connector may simply be logic gates to interface the SFP discrete logics to the PHY GPIOs. The leadless device could be a flash IC.
Presumable the PHY does the I2C talking to the host device.
The SOT-23-6 device is likely a voltage regulator.