Let me expand. There are two SSD interfaces to the modern motherboard - PCIE and SATA. A SATA SSD is the traditional SSD, roughly 3" x 2.5". SATA SSD device nodes under Linux are /dev/sda, /dev/sdb … (quite unfortunately, same as the USB device node series). Micro-ATX motherboards have four SATA ports, while ATX motherboards have six.
NVME SSDs (roughly 3.5" x 1") - the newer kind of SSDs which are roughly 3x faster - are not hooked to the SATA ports. They are instead placed in a dedicated slot on the motherboard that connects to the PCIE bus. NVME SSD device nodes under Linux are /dev/nvme*. Micro-ATX motherboards have only one NVME slot, while ATX motherboards have two.
It is quite normal for a PC to have one NVME SSD and multiple SATA SSDs.