Omega Balance is a concept coined by Anthony Hulbert in his book of the same name, which I've reviewed here.

It's similar to the omega-6:omega-3 ratio, but expressed as a percentage instead: the percentage of omega-3 fats to the total polyunsaturated fats (omega-3 + omega-6). A good Omega Balance in Omega Quant tests is considered to be anything above 15%, with many of the long-time PUFA avoiders being over 20%.

Omega Balance can be heavily influenced in the short-term by consumption of fatty fish like salmon or sardines, or by fish oil supplementation. A healthy person who is at ancestral levels of linoleic acid intake & adipose tissue should have a good Omega Balance even without any fish intake. Read my review of the book

Delta-5-desaturase, also called FADS1 (fatty acid desaturase 1), is an enzyme that converts dihomo-y-linolenic acid (20:3 ω-6) into arachidonic acid (20:4 ω-6) by adding a double bond at the 5 position. Calculating the ratio of its output (AA) divided by its input (DGLA) can be used as a measurement of its activity level. Read more on Wikipedia

Delta-6-desaturase (also known as linoleoyl-CoA desaturase) is an enzyme that converts linoleic acid (18:2 ω-6) into gamma-linolenic acid (18:3 ω-6) by adding a double bond at the 6 position. Calculating the ratio of its output (GLA) divided by its input (LA) can be used as a measurement of its activity level. Read more on Wikipedia

Delta-9-desaturase, also called SCD1 (stearyol-CoA-desaturase 1) or DI18 (desaturase index 18), is an enzyme that converts the saturated fatty acids stearic acid (18:0) and palmitic acid (16:0) into the monounsaturated oleic acid (18:1) and palmitoleic acid (16:1) respectively, by adding a double bond at the 9 position. Calculating the ratio of its output (OA) divided by its input (SA) can be used as a measurement of its activity level. Read more on Wikipedia

Defined as palmitic acid (16:0) over linoleic acid (18:2 ω-6), DNL measures how much fat your body is generating.