Hi and welcome from New Zealand. Glad you have found us! As UnderstandBlue says, an insert is usually the bit you write on. They can also be called internal sheets. I use ordinary copier paper which I cut to fit into the card and I write the greeting or message on it before I stick it in so if I mess it up, I haven't messed up the whole card! I put a single strip of double-sided tape down one side of the insert and stick it where the fold of the card is. There is an excellent book for beginner card makers called The Complete Guide to Card Making by Sarah Beaman. Do you have access to a library where you are? I get a lot of card making books from the library. If you can't get hold of the book I would be happy to scan and email the page on internal sheets for you. We can exchange email addresses via the SCS personal message system if you want.
To live a creative life, we must lose our fear of being wrong. Joseph Chilton Pearce