This is the outer portion of the adrenal gland; it secretes hormones such as hydrocortisone (a glucocortoid) and aldosterone (a mineralocorticoid).
Glucocortoids help cells synthesize glucose, catabolize proteins, mobilize free fatty acids, and inhibit inflammation in allergic responses. Mineralocortoids regulate the levels of minerals such as sodium and potassium in the blood.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.