Folate, Folic Acid, Folacin. What is the difference between the various forms of folate?

The ESHA nutritional database provides data fields for four different forms of folate, listed in micrograms.

Folate:  The Folate field lists total folate, from food and synthetic sources. 
Folate = Folic Acid + Food Folate

Folic Acid:  The Folic Acid field lists the amount of nutrient present in the synthetic form. Synthetic folic acid is seen in fortified foods, and in vitamin tablets and nutritional supplements.

Food Folate:  The Food Folate field lists the amount of nutrient present naturally in food.

Folate DFE:  The Folate DFE field lists the Dietary Folate Equivalents. This is the field used by the DRI folate standard. It is a calculated field based on the following formula:
Folate DFE = Food Folate + (1.7 x Folic Acid)

In 2016, U.S Nutrition Facts labels updated the unit used to report Folate.

On the 2016 Nutrition Facts label, total Folate is reported in mcg DFE; Folic Acid is reported in parenthesis in mcg.

On the 1990, U.S. Nutrition Facts label, Folate is reported in mcg.