It's "down to earth" (no "the") and it means normal, without pretense or artificial airs. You'll find me very down to earth, for example. No bullshit.
"State-of-the-art" is usually an adjective phrase (and then therefore should be hyphenated!) and simply means as up to date as it can be. It's very overused. Everyone says their whatever is "state of the art" when of course, it just means it's the best they could afford when they bought it.
In advertising lingo, it's a filler word. Learn to disregard such phrases. Like the British, for example, love to slap "fully" and "luxury" on everything. Their shops are "fully" airconditioned and their fruitcakes are "luxury fruitcakes." Same old fruitcake, one pound more expensive.
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