What happens to all the information, old Texts etc on my Iphone if i sell it?

I have just got a new Iphone and of course a new sim when i activated it the other one is blank now. I was thinking of selling it or giving it to my sister, but i'm wondering would all my contacts and old Texts still be on the phone when she would get her sim in it and activate it?

Added (1). OK lets put it this way, i will be taking my sim out of my old iphone 5, as i did get a new one along with my iphone 6. So that is the one i used. Now if i give my iphone away or sell it, and the sim is not in it. And the person makes an itunes account for the phone i give them, will my text's still be in it?

If you don't restore the phone through iTunes then yes of course all of that data will still be there.

Also you don't have to get a new SIM for every new iPhone or any phone for that matter (assuming you are sticking with the same carrier). For instance I used the same SIM in from 2003-2012 & only switched it cause I had cut it from its original miniSIM size to microSIM to work in my new (at the time) iPhone 4 & couldn't cut it down further to work as a nanoSIM for my again new at the time iPhone 5, though I still use that SIM for my current iPhone 6.

Always wipe your phone before giving it away or selling it.

OK lets put it this way, i will be taking my sim out of my old iphone 5, as i did get a new one along with my iphone 6. So that is the one i used. Now if i give my iphone away or sell it, and the sim is not in it. And the person makes an itunes account for the phone i give them, will my text's still be in it?