The piece you’re listening to is title The Swan. It was composed by French composer Camille Saint-Saëns in 1886 as part of the musical suite The Carnival of the Animals. A staple of the cello repertoire, this is one of the most well-known movements of the suite.
Saint-Saëns regarded The Carnival of the Animals as a piece of fun, and specified that it not be published during his lifetime, except for The Swan. He saw The bigger piece as detracting from his “serious” composer image. Carnival has since become one of Saint-Saëns’s best-known works, often played by the full string section of an orchestra.
The most typical arrangement for this piece includes two pianos and cello: the lushly romantic cello solo (which evokes the swan elegantly gliding over the water) is played over rippling sixteenth notes in one piano and rolled chords in the other (said to represent the swan’s feet, hidden from view beneath the water, propelling it along).