Fast or exact
Fast mode copies the video without re-encoding, so it is done almost instantly and keeps the original quality. Because video is compressed in groups of frames, the cut starts at the nearest key frame, which can be up to a second or two earlier than chosen. Exact mode re-encodes the selection so it starts precisely at the frame you picked; it takes a little longer.
For most clips, such as removing the first seconds before a presentation starts, fast mode is perfect.
No upload, no watermark
The video is played and cut inside your browser. Nothing is uploaded and nothing is added to the video, and the cut keeps the format of the original file.