An exocrine, or ducted, gland secretes a substance outside the body or into the digestive tract (technically outside the body), as opposed to the endocrine glands, which secrete substances into the bloodstream.
Exocrine glands include:
the salivary glands
the prostate gland
the mammary glands
These are just the most obvious, and there are many more. The substances they secrete perform many different functions, from cooling the body (sweat) to digesting food (pancreatic juice).