There are literally hundreds of thousands of people who have these tiles on marble geometric sculptures at the entrance to epcot. You basically get a picture taken of you and your loved ones together which is later etched into a small square on one of the sculptures. You are basically "leaving a legacy" of yourself for others to view.
I thought it was sort of silly at first, but it was offered as an option with a package we purchased last time we went. We were given 2 copies of what our etching would like and the block and location to look for it when we return. It takes a month or more for your etching to show up, so the whole thing I guess is sort of a gimmick to get you to return and look for your "legacy" at a later date. However, I must say that there was something very nostalgic about having our pictures taken and knowing that they were going to be a semi-permanent part of the park. (I say "semi" permanent because I believe they have determined a date at some point in the distant future when these blocks will be removed.)
Anyway, it didn't take a lot of time, and if you are going back anyway, it seems like a fun thing to do. I can't wait to check out our picture when we get to Epcot in June!