When standing on Earth we experience a frame of reference that is accelerating upwards, causing objects in free-fall to move along parabolas, as seen in the accelerating frame of reference on the left.
I'm trying to understand what is meant by this. When I drop an item on the floor it goes there in a straight line, not a parabola. Same if I drop something from a helicopter. Obviously I'm missing something here. Can someone with more insight ELI5 this to me please?