As human beings, we have evolved to walk on two feet, however bad posture, repetitive sports and simple genetics can lead to schmerzende fersen which gradually become worse if not attended to.
Most problems with feet come from wearing incorrect footwear. Footwear which is either too big or too small does damage to our feet and makes walking uncomfortable. One common issue, is where one foot is bigger than another one, but shoes are issued in a standard size. If you know that one foot is slightly bigger than the other, you should explain this before you buy shoes.
For those people who exercise, the commonly known "athletes foot" can be a problem. The hot and humid conditions that can build up in a training shoe over a period of intense exercise can cause this if not looked at. Treatment is simple and necessary to prevent it spreading to other people whilst in shared showers in gyms for example.
Problems with in-growing toenails can also arise from a combination of the above and so it is important to keep toe nails trimmed to prevent some long term damage. It is normally more common amongst youngsters but does happen to adults as well.
If you have serious problems with your feet, then it is advisable to visit a specialist known as a Podiatrist. They have studied in depth the solutions to both common and rare problems with feet, and for sporting injuries, are by far the best people to see.