A sublevel is known to be the division of the different principle energy levels. There are different sublevels that are available but not all of them will be stated. They are just known as s, p, d, and f. Do remember that the sublevels may be infinite. An orbital is the subdivision of the sublevel.
This may also refer to the space that is most likely to acquire an electron. For example, in sublevel 4, it will come with 16 orbitals. There are no defined boundaries when it comes to orbitals but you can be sure that the regions around the nucleus will be dedicated to the potential electrons that may occupy that certain space.