What does the share button do in the wardrobe?

It saves your clothes in the "share" tab so you can use the same avatar again in the future if you wish. c:

Thank you. I just wanted to be sure because I was worried it would send annoying pings to the people on my friend list whenever I change my out fit. XD

no, it doesn't ping anyone :) You can also use Share if you want an outfit as an image, say to post to an HA contest thread. Click the "View on Subeta" link

Cool. Thanks. :)