In chemistry, the letter s is both the fourth quantum number, and the first orbital. Although they are closely related, they have very different contexts.
s, as the fourth quantum number, represents the spin an electron has. It can have one of two values: +1/2 or -1/2. Two electrons in the same orbital must have opposite values for s.
s, as the first orbital, is spherical in shape. Electrons enter the s orbital in groups 1 and 2, as well as with He. s orbitals can form sigma bonds.