Orbitals are representations of the shape of space occupied by the atom's electrons. Thus, an orbital does not exist on its own as such. The orbitals of an atom are not "there", waiting for electrons to occupy them. Instead, think of an orbital as a representation of where the electron spends most of its time relative to the nucleus.
In fact, an orbital is a probability distribution, and tells us only the probability of finding the electron within a certain volume of space. Typically, we draw orbitals which show us the space in which the electron will be 95% of the time.
Each orbital in a many-electron atom can hold a maximum of TWO electrons.
Thus, in large atoms, there are many orbitals. These orbitals have
structure in terms of size, shape and orientation to one another.