Feeding vs. Fertilizing? and what to use?

Sorry for adding yet another fert question post... but I searched and couldn't find the answers I'm looking for...

Ok so I've read a few places that while fertilizers aren't going to be that important until at least after a couple weeks into growth, I should be feeding my plants regularly? ...wtf? What's the difference? What should I be feeding my plants??

Also, I'm no botanist, but I've taken a few semesters of environmental science. It seems like basically ...nitrogen good for fast development leaves etc. ...phosphate good for root development, and potassium aids in reactions carrying nutrients through the plant.

Based on that, it seems like to start off the most important nutrient would be phosphate to establish a healthy root system. Nitrogen I guess can't hurt but doesn't seem like it's necessary in any kind of high doses for a while ...and potassium doesn't seem like it'd matter untill after I have significant growth. Yet everything I've read says to start with something like 20-5-8 ...15-5-10 etc.

Everything I've read seems like waay too much nitrogen and not enough phosphate...

And then I've seen like 10-15-10 for flowering ...which just seems backwards...

I was thinking 5-15-5 for vegetative, 17-17-17 or something similar during flowering ...do I have it completely wrong?

Thanks for the help guys.

Fertilizing IS feeding. For vegetative growth you need Nitrogen and less Phosphate, a steady dose of potassium is ideal. And for flowering you will need less Nitrogen and more Phosphorus and same levels of Potassium.

From what I understand in veg you want something high in nitrogen and not too high in others something like 5-5-5 i heard will do the trick. In Flowering you want something with more phosphate for example 5-15-5 or something IDK on the flowering though havent been there yet. I'm currently using 15 5 5