The definition of A, B or C Class shares can vary by the mutual fund. Generally though it is a way to have different fee structures which would be tailored to short, mid, and long term investors. The short term class would have no or low front of back load (the fee you pay to buy or sell the fund), but the annual management fee would be higher, while the long term class would have a front and/or back load but lower annual management fee. They also sometimes have different minimum investments as well. In some cases you can convert from one class to another if you’ve been in the fund for a certain amount of time. You will need to look at the fund prospectus to determine the terms for the particular fund you are interested in.