do laptops have 2 ssd slots

I have recently added 2 m.2 SSD cards to my Alienware 15 R3. However, i see there is another m.2 SSD slot available. This slot is labeled SSD-1 and is smaller than the other two m.2 slots.

SSD Memory sticks can also be installed in laptops without a dedicated SSD slot by replacing the Optical Memory drive with a SSD holder caddy.

Hence, people often ask how to add more M.2 SSD slots or a second SSD if their motherboard only has a single M.2 slot. ... But first check for how many M.2 Slots do motherboards have.