The piece is called "Cello Melody"
This is called a portato marking.
In your example, the portato is notated with staccato markings (the dots) along with tenuto markings (the dashes). In addition to this notation, you'll also occasionally find portato notated as staccato notes within a larger slur (instead of including the tenuto markings).
For strings, it indicates a slight articulation of each note while still being within a single bow stroke. For other instruments, it's often described as a "pulsing" articulation. I recommend imagining yourself as a string player, and really envisioning what it would be like to play the notes with a single stroke while still adding in a slight articulation for each.
Further reading is available on the Wikipedia page for portato.
Somewhat of contradiction in terms, seemingly!
Staccato (the dot) meaning to be played fairly short - around half the shown length - while the line means hold the note for at least its full duration!
That said, in string playing, there's slight separation of the notes - even more confounding - but I guess this isn't for string playing, even given the 'Cello melody' title, as three simultaneous note playing is rare there. However, on stringed instruments, it is played making the melody line with the same bow direction, with a slight gap between each note. Not particularly applicable here, with triads on piano.
Named - loure.