The s subshell has 1 orbital that can hold up to 2 electrons, the p subshell has 3 orbitals that can hold up to 6 electrons, the d subshell has 5 orbitals that hold up to 10 electrons, and the f subshell has 7 orbitals with 14 electrons.
s, p, d, f and so on are the names given to the orbitals that hold the electrons in atoms. These orbitals have different shapes (e.g. electron density distributions in space) and energies (e.g. 1s is lower energy than 2s which is lower energy than 3s; 2s is lower energy than 2p).
So for example,
a hydrogen atom with one electron would be denoted as 1s1 - it has one electron in its 1s orbital
a lithium atom with 3 electrons would be 1s2 2s1
fluorine has 9 electrons which would be 1s2 2s2 2p5