Thank you for your question. It is one I answer almost daily as I know it can be confusing.
Green Gables Heritage Place, operated by the Prince Edward Island National Park is the location for "Anne's" house, walking trails and museum. I always recommend to our guests to start the tour at the L.M. Montgomery Homestead. This is the location where the author wrote the book. You will have an opportunity to re-step her actual walks to Green Gables which is the setting for the book. If you prefer not to walk the short trail from the Homestead (it is about a 4 to 6 minute walk) to the Haunted Woods entrance to Green Gables you can drive from site to site in less than 2 minutes. While at the Homestead I would also suggest taking the 1 minute trails to the Green Gables Post Office where LMM, the author, was the Post Mistress. It offers a lovely free museum.
Once leaving the Homestead by car you will turn left out of the lane, go through one set of lights and take an immediate right by car. It is this site where you will view the house and the beautiful avenue of trees.
The other site, the Anne of Green Gables Museum and Matthew's Carriage Ride at Park Corner is also lovely and only a short 15 minute drive from the house. It is the location of the author's cousins and where she was married. They also have a lovely museum and carriage ride along the beach. On the way to Park Corner, you will have an opportunity to visit the author's home where she was born.
I hope this helps clarify and wish you a most wonderful experience on our beautiful Island. In closing, I have one last tidbit of advice. I would suggest also driving inside the National Park at Cawpore Lane in Cavendish and then turning left on to Terre Rouge. You will come to a parking lot at Ocean View located on your right. Words simply can not describe this beauty. So much of when you read in the "Anne of Green Gables" novel published one-hundred and nine years ago is as it was when it inspired LMM to write the story.