Those are magnifying glasses. They idicate if the field has been set for "inlucde in quick find". A green icon is the local table, yellow is a related table. Local table searches will generally be quicker than searching on a related table. Disable the fields you don't need included.
Thank you Mr. Zakary! I've been searching for six months and to think that the question was answered in five minutes by this forum! I am pleasantly impressed!