For a baptism of a baby the grandparents and other relatives and friends are invited. You can buy ready made invitation cards for the christening or baptism, but such cards usually look very classic and not very personal. Invitations for baptism can also be made by yourself. A nice idea is to take a picture of the baby and write some texts and phrases on the back of the picture and send it out as an invitation. You can either label the photo directly using your computer or edit the photo and add some text. When you make your own cards you should keep in mind to use the format of a postcard so you can put it easily into a standard envelope.