That soft spot is where the baby's skull has not formed yet.

Here's a fairly straightforward answer from ZeroToThree.org: "Don't be afraid of the soft spot The soft spot ("fontanel") represents the area where the unconnected skull bones come close to each other, but don't actually attach. The area between the bones ("the soft spot") is lined with a tough, canvas-like material that protects the brain. This lack of bony attachment allows the brain to grow without impediment (if the bones were attached, the skull would not expand to meet the burgeoning size of the exuberantly growing young brain). Caregiving Implications: De-mystify soft spot: "Here is where the bones haven't come together yet. Here, feel it! You don't have to be careful. You can't hurt your baby by touching it! Clean it, wash it, do whatever; it's not a problem!" Explain why it's there: "It's a good thing your baby's skull bones aren't attached to each other. As her brain grows, the bones need to expand too. If there were no soft spot, the attached bones would prevent the brain from growing. Over the next few years, your baby's brain is going to grow faster than any other time of her life! And brain growth means a richer, more active brain. So the soft spot is a nice reminder of how much growing your baby's brain is going to do and why the bones can't attach to each other until most of that growing is done." http://www.zerotothree.org/brainwonders/ped_2week.html So, there's no danger in touching it, even applying a little pressure. The normal care taken for the rest of the baby will be sufficient protection.

It's what people call the soft spot. The skull bones aren't completed connected at birth.

Just to add to what others have said the fontanel is not to be touched .

From what I heard, its a spot that is tender to touch with too much friction. If you look closely, it practically beats.