What is 60i?

This is a frame rate - the number of frames a camera shoots per one second. "60" is the frame rate and "i" stands for interlaced. However because the frames are interlaced there are actually only 30 frames per second. 60 are the interleaved fields that are shown together in one second for smoother video.

Other frame rates are 30p, 24p or 25p where the number are the frames per second and "p" stands for progressive.