What is the meaning of an 8 followed by a dotted line?

Question

There is a 8 and a bunch of dots going over the notes. it doesn't look like octave lines, though.

Answer 1

It's an ottava-line. Or shorter: an 8va line. It means you should play those notes one octave higher than notated.

There's also an 8vb-line (ottava bassa) to play the notes an octave lower, which is drawn underneath the staff.

And then there's the same for 2 octaves too: 15ma and 15mb Which stands for 'quindicessima' and 'quindicessima bassa' or a 15th up or down respectively.