How do rockets reach orbit?
Getting to space is easy; staying there is hard. Why rockets turn sideways, why they drop stages, why launch sites are where they are, and how boosters land again.
Up is the easy part
Space starts around 100 km up, but reaching that height is not enough: anything that only goes up falls straight back. To stay in orbit you need a sideways speed of about 7.8 km/s. Most of a rocket's fuel goes into that sideways speed, which is why rockets rise vertically for a short while and then tilt over in a long arc.
Stages
A rocket is mostly fuel. Once a stage's tanks are empty, carrying them farther wastes energy, so the stage drops away and a smaller engine continues with a lighter vehicle. Two or three stages are typical; Korea's Nuri has three.
Where to launch from
Earth's spin gives a free boost to rockets heading east, up to about 465 m/s at the equator, so many launch sites are near the equator with the sea to their east. Launch sites also need empty sea or land under the flight path for falling stages. Korea's Naro Space Center in Goheung launches southward, between Japan and the Philippines, into polar and sun-synchronous orbits.
Coming back to land
For decades first stages were thrown away. SpaceX's Falcon 9 now flips its first stage around, relights its engines and lands it upright on a ship or a pad, and many boosters have flown more than twenty times. Reuse has cut launch costs and is a big reason why so many satellites are launched today.