Steeping is the term we use for letting
eliquid age for best flavor. Many vendors make all liquids to order and with more complicated flavors (especially tobaccos) the true flavor takes time to develop. It's rather like cooking. The longer the ingredients simmer together, the better it tastes.
If you receive a liquid that you don't care for right away, put it up somewhere dark and cool for a few weeks and revisit it. Some liquids like Dekang are made well ahead of time in large batches and are usually steeped before they get to you, but most of the really popular vendors on the forum make each order fresh.
Hope that helps.