XYZ format is the simplest file format available in PyMOL. Minimally, it can consist of an atom symbol followed by three whitespace-delimited XYZ coordinates.

C 1.23 34.2 20.44

or

N   -1.195    0.201   -0.206
C    0.230    0.318   -0.502
C    1.059   -0.390    0.542
O    0.545   -0.975    1.499
H   -1.558   -0.333    0.660
H    0.482    1.337   -0.514
H    0.434   -0.159   -1.479

It is also legal to provide an atom count should you wish to do so.

3
C    0.230    0.318   -0.502
C    1.059   -0.390    0.542
O    0.545   -0.975    1.499