Legends probably predates many current players, and as a result these players have never seen a box or even a single booster pack. Here, then, is a history lesson of sorts.
The booster packs were not very flashy back then and did not feature card art. They were also plastic as opposed to foil, which unfortunately made it easy to determine their contents without opening them.
Legends was only sold in booster packs; even though it was a 310-card set, it did not contain basic land and was not considered a "stand-alone" expansion. Hence, there were no Legends starter decks.
Included in every pack was a "Legends Rules Card" that tried to explain -- in very small text -- the new keywords and mechanics. Such inserts have since been abandoned for "reminder text" on the cards themselves.