While it is very common to see people using the two terms "excretion and secretion” interchangeably, there are, however, some differences between the two. Although, both involve the movement of materials, extraction is more about the removal of materials that have no further utility from the body. In contrast, secretion is more about the movement of materials from where they are secreted to another point.
Excretion is mostly used when referring to the removal of body wastes such as feaces, sweat, tears, carbon dioxide, urine, from the body. On the other hand, secretion is mostly used when referring to the movement of essential materials or substances such as hormones or enzymes, needed in different parts of the body.
However, secretion can also be used for the removal of unwanted materials from the body. Examples of organs that enable excretion are skin, rectum, lungs, etc. Secretion is commonly used with organs such as digestive glands, endocrine glands, etc.