The diluted count is the honest denominator. It adds in employee-stock-options, unvested rsu grants, warrants, and shares that would appear on conversion of a convertible-bond. Companies report both basic and diluted eps; the gap between them is a measure of how much of the business future dilution will claim.
A gap under 2% is routine. A gap above 15% usually means heavy stock-based-compensation or a convertible overhang that will land on existing holders.
Example: 100M shares outstanding, 9M options, 4M RSUs, and a convertible that turns into 7M shares. Fully diluted is 120M. A $240M profit is $2.40 basic but $2.00 diluted, a 17% difference.
Related: employee-stock-options, convertible-bond, eps