A vented subwoofer differs from a sealed subwoofer in size, as they are often up to twice the size of a sealed enclosure. They are tuned to particular frequencies, which are determined by the size of the hole and the length of the port carrying the sound and air out of the box.
Sealed subwoofers do not allow air to escape. They differ from vented subwoofers because they are great for applications where space is an issue. They are small, comparatively, and are not as loud as vented subwoofers, but deliver clear and smooth bass.
Bandpass subwoofers combine the two types, vented and sealed, in one box. Although difficult to make, the bandpass subwoofer creates smooth, clear bass in a smaller package than a normal vented enclosure. You will need to use specially designed drivers for this type of enclosure.