Swaps and Rollover are two terms meaning the same thing, basically a fee that is applied to any open trade which stays open past midnight.
The fee could be of a positive value, meaning that the corresponding credit will be added to your account at the closing time of the trade, or else it can be of a negative value, meaning that the corresponding credit will be subtracted from your account at the closing time of the trade.
to have more details about Swap & Rollover please visit : What is swap and How are swaps calculated?