At one time, a primary source of transportation through the canals of Venice was the gondola. Motorized transportation has long since overtaken gondolas in practical importance.
The remaining gondola operations cater mainly to tourists.
The prices gondoliers charge their passengers are government-regulated, but don't assume the costs are inexpensive. You can easily pay in excess of $100 USD for a ride that lasts less than an hour, and the costs go up after sundown.
On special occasions, gondola rides make for memorable travel experiences. But be sure you understand the costs before you climb aboard, and make certain you've weighed this expense against other possible splurges in a city where paying too much for gondola rides is a common mistake.