Yes it can be planted, it looks like some kind of opuntia. And that purple thing is a fruit that's probably got seeds in it. I would get some cactus soil and put it in a pot with the bottom pad about half way in the soil and probably prop it up with some rocks until it's got some roots to hold it up. You could probably start watering it in about a week after you have got it planted.

Thanks! Can I break off part of it and give to a friend? How do I get the seeds?

Yes you can cut off a pad. I would cut it right were the pads meet make sure the pad you took off drys and callouses over before your friend plants it or it may rot and for the seeds you can probably wait until it drys up so the seeds are developed and it's easier to get the seeds out, you can use a utility knife and cut the seed pod long ways but don't cut all the through so you don't damage the seeds. Good luck

Thanks again!!