What is the difference between a OEM kernel and a HWE kernel?

Both kernels seems to include latest drivers, but I can't find why both are needed or what are their differences. It's confusing!

Solution 1:

An OEM kernel is created by Canonical engineers for specific brand-new hardware that is not yet supported by the (mainline) generic Linux kernel that everybody else uses. OEM is a short-term kernel; users will migrate to the generic Linux kernel when support for that new hardware becomes available.

A HWE kernel is used only on LTS releases of Ubuntu. It's simply a newer generic kernel. In fact, it's often the same generic kernel used in the current interim release of Ubuntu. Example: The current HWE kernel for 20.04 is the same kernel used in 21.04.