Octave practice.. that’s where the pianist brings their hands down on notes an octave (eight notes) apart. The overall results may, or may not, sound impressive depending on the technique. For years, I found octaves daunting. My hands and wrists would lock and sometimes ache. Now, I find octave practice relatively easy. A case of relaxing the thumb in between swipes at the keys. You almost have to imagine that the little finger is in charge.
There’s some excellent studies and exercises for improving all aspects of piano technique, including octaves. These include Czerny’s 160 8-bar exercises op821 and Chopin’s preludes and studies. The final Chopin studies of the second set include a stormy octave opening with a lyrical middle( still using octaves) and a second arpeggio study (no 24) based around a simple but expressive idea in C minor.
For those wanting to take octaves to the limit, try the Liszt studies and Hungarian Rhapsodies, or anything involving lots of octaves. I happen to love ragtime and Scott Joplin.