"Throttle" has one meaning, but it can be used in a number of different ways. A throttle "chokes down" a flow of (usually) liquid to reduce the output. So if you had a straw and sucked on it to get a drink; then if you squeezed the straw it would reduce the flow, "throttling" what you are getting to drink.
In a car, the throttle is another word for "accelerator". It's actually in the reverse sense: the more you push the accelerator, the more the engine accelerates - but this is reducing the amount of throttle on the fuel flow.
In aviation and space terms, this word is even further removed from its original meaning. "Throttling up" means pushing forward on the thrust lever to increase acceleration - but in actuality it is actually reducing the amount of throttle on the fuel lines to the engine.
In that specific article (I assume on the "Vomit Comet" to induce a zero gravity experience) it is implying that the throttle is being used to control the aircraft. To climb, you need more power, so you'd throttle up; and to descend, you'd need less power, so you'd throttle down. In short, you'd throttle the plane to control its up and down manoeuvers.
Having said that, they're also probably pulling back on the yoke to climb, and pushing it forward to dive, to more precisely control the plane's position in the climb and dive - but engine power is by far the more obvious mechanism, with the engines by turns screaming and whispering as it moves from full throttle to barely idle.
