24P means the camera captures images as whole video frames, 24 times a second.
60i means that the camera captures images as fields containing every other line of video, two fields to make up a frame, 60 times per second (hence why 60i is also known as 30 frames per second, because there are two fields for every frame of video. But that's not the same thing as 30P, which means capturing 30 whole frames per second.)
When two fields are combined, since each was shot sequentially, one after the other, any moving object occupies a different spot in each field, so when two fields are combined, the whole frame shows a toothcomb effect along the edge of the movement.
With a film camera, the shutter is a spinning disk with a slice cut out to allow light to pass through, and usually it is a half-circle (180 degrees out of 360) so the shutter is open only 50% of the time. So at 24 fps, the shutter is closed for half of 1/24th of a second, so the exposure time is 1/48th of a second. The low frame rate of 24 fps, combined with the shutter being closed half the time, gives motion that unique strobey look we associate with film.