What is the difference between a 1909 vdb and a 1909 vdb s penny?

A lot of money and 4,000 miles.

1909 VDB cents were struck in Philadelphia and retail for about $7. Like all Phila. coins before 1979/80 (except for "war nickels") they do not have a mint mark.

1909-S VDB cents were struck in San Francisco and have a small S under the date. These are much rarer and retail for $900 to $1500 depending on condition.