Practice is when someone is practicing something on a regular basis. For example, I play the piano. When I take up a new piece, I have to practice it for weeks and months before I can feel good about being able to play it in full. A rehearsal is the final piece practiced before a show or a concert. I hope that helps?
Practice is what musicians do to get the music as close to perfect as they can.
Rehearsals are similar.
The term for rehearsal is generally used for a group of musicians, like a band, choir or orchestra. Practice takes place in rehearsals as well, when the conductor goes over and over a certain section of music.
Ah, thank you for this answer, TheCranberryBarn. Now I understand why the choir director uses "practice" because her goal as a musician is to get it as close to perfect as possible. The "rehearsal" definition very helpful.
The way I look at it, practice is the honing of your craft even during downtime, like playing the piano at night just to improve your skills.
A rehearsal, on the other hand, implies an upcoming performance of some description and is simply the act of matching the skills you've been practicing with what said performance requires, like learning a particular piano tune in time for a chorus concert. There is also the implication that you might be doing this with your peers, with whom you'll be putting on this performance.