DRTV generally bypasses traditional retail stores to make a product sale directly with the consumer, but can also be used to drive product sales at retail. DRTV is comprised of three primary marketing subgroups of short form, long form and live home shopping.
Persia/Persian is more or less synonymous with Iran/Iranian. Persia is just the older name whereas Iran is the country's modern name. I think people from Iran call themselves Persian because of Iran's negative image in the west since the 1979 revolution.
The majority of the people of Tehran are Persian-speaking people, and roughly 99% of the population understand and speak Persian; but there are also large populations of other Iranian ethnicities in the city such as Azerbaijanis, Armenians, Lurs and Kurds who speak Persian as their second language.