RAM speeds explained

I was wondering about how ram speeds work. i want to buy a FW12 (https://frame.work/de/en/products/laptop12-diy-intel-13gen/configuration/new) and i saw the website lets you select 5600 speed ram but says "will work at 5200" speed, and the link they provide to commpare prices on pcpartpicker opens up a search for ddr5sodimm at 5600. why why the diference, i thought it was just this:

lower number = faster

and match whatever the cpu/MB says you chould get

can you guys explain it better or show me a ecource that explains the difference?

thx in advance