The trade card was essentially an early form of the business card. Typically it listed information on which company it belonged to, where they were located, and what products they sold. It was a way to advertise to already existing customers, as the business owner passed out the cards to remind the consumer of where the they bought their items in hopes that they would return. The reciever of the cards could then pass the trade card to a friend or neighbour to pass on the word about the store.
While the trade card was similar to a more modern business card, their designs were made with the intention of having the receiver keep it. They often had bright and colourful illustrations such as this one, which shows a young girl holding a basket of flowers. It's possible that this card was printed seasonally for Spring, as the blue and pink colours, and the greenery of the flowers depicted are typically associated with the colours of Spring. These illustrations would "promote" the holders of the cards to keep them, since they could be a nice decoration, and because of the intricacy, the holder may be more inclined to keep it. Their bright colours could also catch the eye of someone nearby, and they may ask where you got the specific trade card from, sparking a conversation about the business.
It was a different form of advertising. The trade card didn't necessarily need to have all the store's information printed on because they people whom they were being handed out to already knew where the store was located. It was also meant to be kept in a wallet or pocket, not hung on a wall or printed in the newspaper, making it more of a personal keepsake than public advertisement.