bringing into closer cooperation people interested in all aspects of flags such as their history, significance, specifications, use, and manufacture;
furthering a strong and growing interest in flags as a serious study or as an avocation;
promoting research into the origins, history, and symbolism of flags;
publishing on flags and vexillology;
formulating standards for flag teminology, methodology, and data recording;
studying and providing guidance on flag usage and design through national surveys and guidebooks;
cooperating with other vexillological associations, agencies, and research centers, and foundations; and
representing vexillologists of North America on an international level.
In lieu of the fifth point—formulating standards for flag terminology—their website boasts an "Illustrated Dictionary of VEXILLOLOGY," which is actually not very illustrated. Mostly text, but thorough. I should also mention the dictionary is an "on-going project," so perhaps their web-masters have yet to reach the whole "illustrated" part. They're getting there.
Some terms of note featured in the not-so-illustrated dictionary:
aspect distortion : the effect of distance on the perception of aspect ratio; for example, a flag with an aspect ratio of 1:1 1/4 may appear square at a distance.