In a book I'm reading, the author mentioned the launch of Soyuz spacecraft as follows:
What made it more spectacular was how close we were when it lifted off the launch pad. Yuri, Tim and I were sitting on the roof of the search-and-rescue tower, about 1.5 km away from the rocket. It was gone 3 a.m. on a beautifully clear night and, when I saw the main engines light up, followed by a deep roar a few seconds later, a huge grin spread across my face. But my expression soon changed to one of astonishment. What I had heard so far was merely the engines at intermediate thrust, when there’s a brief pause for a checkout. As the main engines opened up to full power, the noise engulfed me – a powerful rumble of deep bass notes that reverberated around my chest cavity. Just when I thought it couldn’t be any more impressive, the Soyuz lifted off the launch pad and, as it climbed, a deafening crackle filled the air.
My question is: what is intermediate thrust? And what is the brief pause before check out here for?
Does intermediate thrust means that the intermediate part try before starts and then they pause to check everything is okay before launch?