A is the basic, low end boards (A620 for example), these can't do CPU overclocking and are typically best avoided. *Note B840 is effectively in this tier as well though none of those are out yet. B is your mainstream boards (e.g. B650), unlike Intel, AMD allows CPU overclocking on this tier of chipset and can do it just as well as X series boards with proper power delivery and VRM cooling (which plenty of boards have, but some of the low end ones don't). X (X670, X870) is more for people who need more connectivity as these have the dual chipset which can multiplex more lanes. However, this has become a little muddled with the 800 series. More on that below. E on the end (B650E, X670E, X870E) just means that both the primary PCIe slot and at least 1 x4 NVMe M.2 slot are required to be PCIe 5.0 Though X870 also requires this. X870 and X870E have an additional requirement that they must support USB4, keep in mind this means that 4 of the dedicated CPU lanes must now be diverted to this, this is why you see so many of these boards with M.2 slots suddenly sharing lanes with the primary x16 slot. Going back to the X series comment on connectivity. Before the 800 series (for AM5 at least), X670 and X670E boards that the dual chipset chips leading to more chipset bandwidth and thus greater connectivity for whatever the board maker wanted to use it for (higher speed lan, more/faster USB ports, more M.2 slots, etc). However, X870 only has the single chipset chip, while X870E has the dual (note these are the exact same physical chips as the 600 series boards). Thus, X870 is more like refreshed B650E with a requirement of USB4. So basically, for budget minded mainstream consumers B650 is just fine even if you want to overclock. If you also want to ensure PCIe 5.0 support (and do not need USB4) then B650E would be the choice. Obviously if you do want USB4 X870 or X870E is ideal though USB4 is offered on some 600 series boards though it was relatively rare outside of the ultra high end (though there were a few like the B650E Taichi/Lite). If you want maximum connectivity, then you want either X670 (if you don't care about full PCIe 5.0), X670E (if you do) or X870E (if you do and want USB4). Answer from A5CH3NT3 on reddit.com