Individual Lenormand cards generally represent simpler concepts than those represented by a Tarot card, and one therefore generally needs more of them to describe a specific concept. I do not mind this at all, as its simplicity makes Lenormand a very flexible reading tool.
For example: The Knight of Cups Tarot card represents among other things a charming romantic man and a message about relationships and emotions. In Lenormand, such concepts could be represented by Man+Bouquet and Letter+Heart respectively. These card combinations are effectively acting as a noun with a modifying adjective.
Lenormand cards should be read individually and in combination with their adjacent cards, as both approaches can provide useful clues to the meaning of the cards in a given reading.
Most Lenormand books and courses contain lists of card combination meanings that are both helpful and unhelpful. They are helpful in that they show examples of how card combinations work. They are helpful in that they can give your intuition a jumpstart when you are stuck. They are unhelpful in that beginners tend to rely on them exclusively and don't necessarily realize that they are only examples. None of the listed card combination meanings may be relevant, and it is important to learn to combine cards intuitively in order to understand the message in the cards in any given reading. (This is just as well, as otherwise one would have to memorize a gazillion possible card combination meanings in order to give a live reading without referring to the book and looking unprofessional.)
This leads me to the relevance of a particular card combination's order. In some Lenormand systems, the order of the cards in a card combination makes no difference to the meaning of the combination. In the Steinbach system that I use the order of the cards matters, especially when the cards could represent an action.
Coffin+Storks: recovery from a loss
Storks+Coffin: cancellation of an anticipated change for the better
Note that changing the card order in the first example above does not make too much difference, however these card combinations represent nouns not actions.
[Card images: Modern Minimalist Lenormand by Melissa Haney licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License]
[You may also be interested in reading Jason's related blog posts Lenormand Thoughts on Combining Cards (or Not!) and Lenormand Combinations: Order Matters.]