Type may be used in the normal generic sense, meaning a particular kind or category of coin.
It may be used more specifically to mean a particular combinations of legends and designs on a specific denomination.
For Roman coins, type may also be used specifically to describe the design on the reverse. For example, during the reign of an emperor or empress, it is likely that many different coins were struck. Usually, the portrait of the ruler is always displayed on the obverse of the coin. But on the reverse, many different designs or types can be found. To aid in communications between collectors, the reverse type is referred to along with the ruler's name.