The three types of connections are Text to Self, Text to Text, and Text to World. Text to self is about how you personally relate to the book. What can you relate to in your own life or perhaps the life of someone you know that is in the book? Text to Text has to do with comparing what you are currently reading to something you've read before. For example, if you are reading a book about space, you would think of other reading you did about space, maybe another book, an online article, or a blog. Text to world has to do with finding connections in your current reading to the world around you. Is there anything going on in your reading that is similar to what is going on in the world?
I hope you find this helpful!