What is the difference between an endocrine and exocrine gland?

An endocrine gland secretes its products, for example hormones, directly into the blood. An example of an endocrine gland is the adrenal gland which secretes adenaline made in the adrenal medulla directly into the blood.

 

An exocrine gland secretes its products for example enzymes, into ducts that lead to the target tissue. For example the salivary gland secretes saliva into the collecting duct which leads to the mouth.

It's important to note that the pancreas performs both endocrine and exocrine functions. It releases insulin and glucagon directly into the blood (endocrine) and also secretes pancreatic fluid into the pacreatic duct which leads to the duodenum (exocrine).