Basically Compost tea is made by steeping compost in water, let it steep for a few days and you have it. There are many ways to make it, soome complicated and some very simple. CT can be applied as a soil drench of foliar feed. It works by spreading the beneficial microbes of compost throughout the garden.

As to salt in synthetic ferts? Yes they exist, but you don't need compost tea to flush them from the soil. Some good hosings will do that. The CT will initiate some growth in the way vitamins help the body. My own opinion is that CT is not a food but rather a nutriative amendment. Like going to the Dr and getting a shot of B12 or getting your vitamins from a fruit or vegetable which is more substantive than a one-a-day.

That's actually a good analogy for synthetic and natural ferts. A synthetic fert is a like one-a-day for plants. Think of how you feed your own children. Do they eat crappola junk food and you supplement their health with a fred flinstones vitamin, or do you give them sensible foods and lots of fruits and veggies that are the mainstay of their health? The child that gets a good diet with natural nutrient sources is going to stave off malnutrition and disease far better than a child who eats crap and takes a vitamin supplement.