The following comes from the iPhone Human Interface Guidelines, under Table Views, Text Views, and Web Views > Table-View Elements.
Use the Disclosure Indicator button, which contains a gray chevron at a cell’s right, when tapping the button will bring up a list of more choices.
Use the Detail Disclosure button, which contains a round blue button at a cell’s right, when tapping the button will bring up detailed information about the list item. As a mnemonic help, just think of “Detail” when you are revealing the actual details of the choice and not more choices.
UITableViewCellAccessoryDisclosureIndicator; // Adds “>” to right of cell.
UITableViewCellAccessoryDetailDisclosureButton; // Adds round blue button to right of cell.