It is actually very simple to know the difference between the two just based on the name of the accreditation. When you say regional accreditation, this means that the accreditation that will be earned through six regional agencies.
Take note that each regional agency will be for a certain available region. Achieving accreditation for all six can truly be considered an accomplishment. For national accreditation, this means that the accreditation can depend on the different types of schools that have already been accredited.
There are also some specific types of schools that can apply for this type of accreditation. The credits that will be transferred from national to regional will not be accepted in regional schools, but national-accredited schools may accept credits from regional schools.