The beginning of something is the start. The start of the movie may have been a little slow, but by the end you were on the edge of your seat.
As a verb, start means to begin an activity or event. Some people turn to the last page of a book before they even start it, so they'll be prepared for the ending. Start can also mean to move suddenly in surprise or alarm, or to startle. This is actually the original meaning of the word start, which comes from the Old English word styrtan, meaning to caper or to leap up.