Accreditation is when a school or university voluntarily submits itself to be inspected and judged by an accrediting agency. Such agencies then decide whether or not the school and their courses meet a certain standard of quality to be recognised as a valued and respected provider of distance learning courses. Schools that pass this inspection will be awarded with the accreditation and will therefore be seen as a legitimate and well-regarded institution.
This is important if you want to get a widely recognised degree or qualification that you know will be accepted by almost every employer and that can be transferred to other schools and universities.
However, accreditation is not always necessary especially if you are studying for a specific certificate or learning a new skill. In these cases you will probably find that most of the institutions that provide certification courses are not accredited but still provide certificates that are valid and recognised by the companies that produce the certification (i.e. Microsoft). These types of courses usually only cover a specific topic or area such as computer technology or foreign languages, but they are still a great way to get good training and are most often recognised and accepted by employers.
With accreditation there is a problem in that anybody can set up an accrediting agency and can then 'accredit' any school they want, usually for a financial incentive. This means that there are hundreds of false accrediting agencies about, usually called 'accreditation mills', and you need to check that your chosen provider is accredited by a recognised agency.
In the US there are 6 widely recognised and accepted agencies that cover different regions of the country, these are called regional accreditation agencies. To find out if your potential school is covered by one of these regional agencies simply find out the location of the school via their website then look up their name with the appropriate regional accreditor to see if it is on their list of accredited schools in that region. The regional accreditors are:
New England Association of Schools and Colleges(NEASC)
Accredits schools in Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont, Europe, Africa, Asia, and the Middle East.
North Central Association Commission on Accreditation and School Improvement(NCA)
Accredits schools in Arizona, Arkansas, Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Navajo Nation, Nebraska, New Mexico, North Dakota, Ohio, Oklahoma, South Dakota, West Virginia, Wisconsin, and Wyoming.
Middle States Association of Schools and Colleges(MSA)
Accredits schools in Delaware, District of Columbia, Maryland, New Jersey, New York, Pennsylvania, Puerto Rico, U.S. Virgin Islands, Central America, Europe, and the Middle East.
Southern Association of Schools and Colleges(SACS)
Accredits schools in Alabama, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Texas, Virginia, and Latin America.
Western Association of Schools and Colleges(WASC)
Accredits schools in California, Hawaii, Guam, American Samoa, Palau, Micronesia, Northern Marianas, Marshall Islands, and other Australasian locations.
Northwest Association of Schools and Colleges(NWCCU)
Accredits schools in Alaska, Idaho, Montana, Nevada, Oregon, Utah, and Washington.
For international schools and universities you can check the Council for Higher Education Accreditation's website to see if your school is listed with a recognised accrediting agency in that country.