Vitamins and supplements are used interchangeably in the household, but they are not the same. It is important to know their differences to be able to fully utilize them.
In general, vitamins are substances that your body needs in order to grow and develop normally. You get most of your vitamins from the food you eat while some like Vitamin D and K can be produced by the body.
Dietary supplements, as defined by the US Food and Drug Administration, are products that contain dietary ingredients which may also include vitamins with minerals, amino acids, herbs and other substances that can supplement one’s diet.  Supplements are designed to complement the diet, not to replace the food we eat.
There are thirteen commonly known vitamins that the body needs to function properly. These 13 vitamins are classified into two - fat-soluble and water-soluble. Fat-soluble vitamins are stored in the liver. Vitamins A, D, E, and K are fat-soluble vitamins and they can stay in the body for days, or even months. Meanwhile, water-soluble vitamins like Vitamins C and different types of Vitamin B do not stay in the body for long. They are immediately excreted in the urine. This is why these vitamins need to be replaced regularly. 
Sources of Vitamins
Vitamins can be produced by the body but it does not make the sufficient amount needed for it to function well. This is why we need a balanced food intake to get all the vitamins we need for good health. Here are some of the sources of the different types of vitamins:
Dietary supplements come in many forms like pills, liquids, capsules, powders, and energy bars. Popular supplements include vitamins D and E; minerals like calcium and iron; herbs such as garlic; and specialty products like fish oils.
People use dietary supplements for different reasons - some to supplement their diet while some use it to help manage their medical conditions. Some supplements can also help in boosting energy or getting good sleep. It can also be helpful in managing estrogen levels for postmenopausal women.
Supplements are generally safe and beneficial when taken properly. For example, pregnant women who use folic acid supplements reduce the risk of certain birth defects. Another example is vitamin B12 supplement, which is beneficial in people over age 50 who often have a reduced ability to absorb naturally occurring vitamin B12.
However, supplements should always be taken with caution. Many supplements contain active ingredients that have strong biological effects and may not be safe for all people. They are most likely to cause harm when taken instead of prescribed medicines, or when taken in combination with many other supplements. For example, antioxidant supplements like Vitamin C and E might lessen the effectiveness of some types of chemotherapy.
In addition to this, the ingredients found in dietary supplements are already in different kinds of food like breakfast cereals and beverages. Depending on your diet, you may find yourself getting more of these ingredients than you think.
Taking more than you need is also harmful to your health. For example, too much vitamin A can cause headaches and liver damage and reduce bone strength. Excess iron may cause vomiting and may damage the liver.  Extra precaution must also be exercised by pregnant or nursing women.
With this said, it is best to consult a doctor before using any supplement. It is best to know first which products are appropriate and safe for you.
In summary, again here are some things to keep in mind: