Fertility clinics, obviously, specialize in helping people struggling to get pregnant. The doctors at the clinics have more training than normal ob/gyns on identifying and solving fertility problems.
Did your ob/gyn test you and your husband already? Your specialist will probably run additional tests to diagnose and problem and figure out what solutions might work. Possibilities include prescribing drugs, recommending surgery if that might solve a problem, or recommending procedures such as iui and ivf.
Don't worry about the fertility specialist. Just keep in mind that they have more tools at their disposal than your family doctor.