Philatelic mail (as opposed to commercial mail) can be described as any envelope or card being sent on philatelic purposes. Most of them have genuinely travelled through the post, and been franked at the correct rate.
What is worth noting though, is that the motivation behind their sending is stamp-collecting oriented. Whenever you decide to buy such item for your collection, you should be aware of that, as it can (or cannot) impact on the future sale of your item.
As philately developped and grew during the XIXth century, philatelically inspired mail became more common. Collectors wrote abroad to send their stamps for an exchange, or against cash. For Classic Russia, the most famous correspondance known to date is the Breitfuss correspondance (he was one of the giant of Imperial Russia philately).
Figure 1 - St Petersburg to New Jersey, 1879 : "Mr Ackermann, dealer in stamps"
The postal stationary envelope illustrated above has been sent from St Petersburg to USA in 1879 (Figure 1). The 20 kopecks indicium has been correctly uprated with an example of the 1 kopeck adhesive, making it to the 21 kopecks rate (triple rate to foreign destinations in 1879).
The adress is very telling: 'Mr E.K Ackermann, dealer in stamps'. You cannot make it more philatelic! Mr Ackermann was a very famous stamp dealer, and probably one of the first to operate on the American continent. This is a rather early philatelic cover from Imperial Russia. If any reader knows about earlier sendings, please leave a comment.
It is amazing how much trouble the early collectors took to get their hands on exotic material. Remember that, at that time, there was no telephone and that communication between countries, not to mention continents, had an 'epic' taste. Figure 2 illustrates a reply card sent in January 1894 to the Governor of Mozambique (!), regarding the exchange of stamps. The sender apparantly was very eager to get some stamps from the Portuguese colonies.
Figure 2 - Odessa to Mozambique, 1894 : Regarding the exchange of stamps
This phenomenon of early philatelic covers is not, of course, limited to Russia itself. All the major countries, especially in Europe, had their share of philatelically-oriented mailings. But some of them are scarcer than others.
Figure 3 illustrates a very scarce envelope sent from Kahuta in the Indian State of Poonch, franked with a combination of Indian stamp and the local Poonch 2 annas issue. This envelope is part of the well-known (well, at least for the specialists...) J.C Bechtler & Co philatelic correspondance, based in Allahabad. The Indian State of Poonch was located in the area of Jammu & Kashmir. Definitely not a developped, greatly populated industrial area in 1892!
Figure 3 - Poonch to Allahabad, 1892 : philatelic cover from a mystical area!