trade cards have illustrated advertising for a Company

  
Trading cards have to be bought = were bought = are for sale in sealed packages
and are edited in sets mostly related to sports events or "playing" game

Trade cards on the contrary were a gift from a Company and are really 50 to 150 years older,
 these days it is to costly to give away cards, so only an illustrated visiting card or postcards from a company, printed with their address AND/OR product publicity, could be called a trade card

Furthermore a trade card has printed information about the Company on front AND reverse
As always there are exceptions : if the printer used the cards ( which he printed ) for other purposes.
Then we can find the trade card without printing on the back and call it a printers proof.
If there is NO printed advertising on the card nor on the front nor on the reverse side then it is called a stock card.

Most trade cards were produced in sets ( mosty 6 cards ) by very big international Company's, those were the first multi-nationals
Good examples were the big Tobaco Companies beginning 1880, big tea and coffee distributors (Arbucles), chocolate ( Suchard, Van Houten ),  meat extract company Liebig,  Cibils and many others.   Serials ( series, sets ) were edited sometimes on 100.000nds  from each set.  And the biggest collection is that from more than different 2000 sets ( +7000  variations in many languages  ) by Justus von Liebig's Fleish extrakt Kompagnie. The earliest lithographic color card ( stone press print ) I have is a Rimmel Parfume card from 1862.  Of course there are known earlier cards ... porcelain cards : ...  but those were individual name cards from shops AND not editied in sets, this was around 1837 ( my oldest )

I just wanted to make clear the difference between trading cards  :newer ( mostly after WWII, smaller, coated, offset = 3 colors or laserprint printed, no publicity for an editing food-, drug- or product company )
and
trade cards :  older; smaller sets of 6 or multples of 6;   litho, litho chromo, chromo litho = real color up to 8  (sometimes 17 colours ); always advertising a product somtimes lifted, floating,  playing in the scenic  image; mostly stories ( first comic stories ); sometimes with pricing or real misleading, suggesting topic to buy the product !
victorian advertising trade cards

trade cards are mostly found glued in very old albums or iserted in albums especialy edited for that purpose by the company's advertising department