TEA is produced from Camellia sinensis cultivars (tea plants.) The six types of tea are black, dark (puer is a sub-category of dark), oolong/wulong, green, white, and yellow. Teas can be purchased either decaffeinated, or caffeinated.
An HERBAL BLEND might very well contain caffeine if it is made with Mate/Yerba Mate (Ilex paraguariensis), Yaupon (Ilex vomitoria) or any of the six types of tea, because by definition, plant material is considered herbal. Herbal blends contain a mix of dried herbs, berries, fruit and spices, and can sometimes be a combination of those with tea, mate, rooibos, or yaupon.
A TISANE is a beverage which contains NO caffeine and is made only from dried herbs, fruits, berries and spices. It can contain plants having medicinal properties.
But really, I don't care if you call a tisane herbal tea or an herbal tea tisane. You can call it ALL tea, and that's okay by me. The point of this article is to understand which products might contain caffeine.