Purple and its lighter lavender shades has a special, almost sacred place in nature: lavender, orchid, lilac, and violet flowers are often delicate and considered precious.
While purple is the color of royalty, lavender is the color of femininity. It's a grown up pink.
Use the color lavender to suggest something unique or extremely special but without the deeper mystery of purple. Lavender may be a good choice when you are targeting women and want to invoke feelings of nostalgia or romance.