ALL and * include all the atoms.
ATOM selects atoms by name. Likewise, CELL selects tags by name where the tag substitutes for the atomname in the syntax.
RESNAME selects by residue names (eg, GLY, TRP, etc.)
RAMA selects atoms by IUPAC name and residue name.
RANGE allows for a selection over a range of atoms.
BYNUM allows for a selection by number.
AROUND will add to the selection all the atoms within the distance specified of the atoms currently selected.
COOR will select those atoms whose coordinate component satisfies the given relationship to the number specified.
CONTACT and SURFACE will compute the accessible contact area or surface, respectively, for each atom and will mark all atoms whose value exceeds or equals the cutoff. The probe gives the size of the probe. If zero is used for the probe, then the current default probe size will be used (typically 1.4 Angstrom).
BYRES will include all the atoms in every residue for which at least atom has already been selected.