memes

Technically, it does provide better connection speeds by enabling the router to avoid channel hopping, so it can talk to multiple devices (or the same devices if it has multiple antennae) at the same time. This is part of the recent wifi6 and wifi7 standards so more and more devices will start to gain speeds using this technique

Realistically computers have at best 2 antennae and this is largely marketing wank.

Lord Sauron would like a word.

It does. Wifi uses MIMO (Multi-in, multi-out) to run multiple concurrent data streams over the same channel width, which overcomes individual channel bandwidth limitations (there's only so much radio frequency space to go around). Each stream having its own antenna, and having larger antennas, gives stronger signal/noise ratios, less retransmitted packets, and overall better connections.

A lot of those high end "gaming" routers are often oversold though.... MIMO improves throughput if you have an Internet link it can saturate; realistically even a midrange 2x2 802.11AC router will provide more wifi bandwidth than your internet does. And for gaming, they do nothing to improve latency no matter how many streams you run, as wifi's inherent delay (5-15ms) is pretty much a fixed quantity due to its radio broadcast time-sharing nature. The meme is correct. A $6 ethernet cable beats any and all wifi routers and client adapters, and always will.

I believe it's for beam forming which can be used to improve signal strength in a specific direction.

Still cheaper

Impressive, I lose half my speed with the router around the corner.

Your PC probably has poor antennas and/or WiFi chipset. The pc might also be located in a worse place