Earphone definition, a sound receiver that fits in or over the ear, as of a radio or telephone. See more.
Answer Wiki. If a rocket went straight up, it would either continue in that direction and leave Earth, or it would fall back down, depending on its velocity. Most rockets intend to enter orbit, which is an elliptical trajectory, and it's much more efficient to arc into this trajectory than to go straight up and then accelerate laterally.
Initially, it goes straight up to get through the densest part of the atmosphere as soon as possible. But by the time it is in orbit, it needs to be going horizontally. So somewhere along the way it has to have completed a 90 degree turn. At each point along the way up, there is a choice of how much of the rocket's thrust to put into getting up and how much into getting going horizontally.