Share Classes (A, B, or C) determines what fees (load and expense ratios) you pay to own mutual funds
Class A shares charge load when you purchase & have lower expense ratios
Class B shares charge load when you sell & have higher expense ratios, but convert to A-shares if held for several years.
Class C shares have higher expense ratios than A-shares & a small exit fee, which is usually waved after one year
load aka: upfront or exit fees that can be waived if you ask
expense ratio: the amount mutual fund companies charge investors to manage the fund.