What will happen if I mix DDR4 RAM and DDR5 RAM in my PC?

I've tested the best DDR4 and DDR5 RAM to find the right kits for you ddr4 and ddr5 same slot I recently build my own PC, with a Z790 motherboard a intel i5 13K Alder Lake and a single 32 gb DDR5 ram stick When trying to install ddr4 in ddr5 slot DDR5 Memory or DDR4 RAM? 3600Mhz or 6000MHz? What should you buy for gaming, on

ddr4 sodimm slot DDR4 and DDR5 RAM sticks are installed in pretty much the same way, but they're not cross compatible Even though some CPUs might work with both