Can you explain what is the difference when you see these two categories on intel.com?
What should I buy? a chipset or a motherboard?
I'm completely failed to understand if it is one and the same thing.
An Intel Chipset is found on a variety of Motherboards from different suppliers. The chipset covers all the BIOS requirements of the Motherboard. It normally consists of the North bridge and the South bridge chips. North bridge interacts with things like the RAM and the CPU and the South bridge interacts with the SATA controllers amongst other things.
Intel also make Motherboards of their own. So you can end up with an Intel Motherboard with an Intel Chipset or something like an ASUS or Gigabyte Board that has an Intel Chipset. ASUS etc also make boards with the NVIDIA chipset for example.
So an Intel Motherboard is a board actually made by Intel other suppliers make different boards with the Intel Chipset but named with the suppliers brand name.