It was actually called the Home Farm. Her father rented it from the Baron, farming it for hundreds of years and so, her father said (quietly, sometimes, after he'd had a beer in the evenings), as far as the land knew, it was owned by the Achings. (1.59)
The chalk is something that Tiffany's grown up on her whole life, and that her ancestors grew up on too. Miss Tick said the chalk was made up of many, many tiny ground up bones—and it seems like the land is in Tiffany's bones too.
Tiffany shared a bedroom with Fastidia and Hannah. She woke up when she heard them come to bed, and she lay in the dark until she heard their breathing settle down and they started to dream of young sheep shearers with their shirts off. (3.25)
Even when she's sleeping Tiffany doesn't get much privacy. Their home is cozy, but the family members are definitely always in close quarters. Can you imagine how dreamy having her own room would be?
She drifted off to sleep again, thinking about the land around the farm. She knew all of it. There were no secret places that she didn't know about. (3.47)
The chalk is so familiar to Tiffany that there are no places that she isn't aware of. She's spent her whole life exploring this area, and she's more comfortable with it than anywhere else in the world.
"Anyway, lots of warrior tribes think that when they die, they go to a heavenly land somewhere," said the toad. "You know, where they can drink and fight and feast forever? So maybe this is theirs." (6.24)
The pictsies have their own idea of what it means to go home after you die. They think that they're currently dead and in heaven, which isn't so different from thinking that you're alive and going to heaven, if you think about it.
But her Second Thinking said: He's mine. My place, my home, my brother! How dare anything touch what's mine! (8.168)
Even though Tiffany isn't the best big sister in the world at the beginning, she makes it up by going to save Wentworth. After all, he's a part of her home and she needs to bring him back to her family. It's her duty.
Tiffany dropped the pan and swept him up in her arms. "It's Tiffy," she whispered. "And we're going home." (10.154)
When Tiffany does find Wentworth, all she wants to do is to get him home again. She doesn't want to explore anymore; she just wants to make things right at the Aching homestead.
A drome was sitting on the rocks with its pale, fat legs sticking out in front of it. It was staring out to sea and didn't appear to notice the approaching boat. It thinks it's home, Tiffany thought. I've given it a dream it likes. (12.105)
The dromes caused her a huge headache earlier, but when Tiffany sees the one staring out at sea, she can't help but feel bad for it. It's obviously homesick, and the Queen must have dragged it here from somewhere.
"Stay away from here," said Tiffany. "Never come back. Never touch what is mine." (13.158)
Tiffany's not going to put up with the Queen coming willy nilly into her world whenever she feels like it. Nope—this is her land, and she's going to protect it no matter what it takes.
Her mother had insisted on Tiffany's going to bed, even though it was broad daylight. Actually, she didn't mind. She was tired, and lay under the covers in that nice pink world halfway between asleep and awake. (14.169)
Coming home is rather nice after a long jaunt through Fairyland, even if it means that your parents are going to boss you around again. We guess home really is where the heart is, huh?
"And in a while, maybe, I won't be here and you'll wonder: Where is she? But part of me will always be here, always. I'll always be thinking about this place. I'll always have it in my eye. And I will be back. Now, go away!" (14.257)
When Tiffany talks to Roland, she warns him that she'll always be around to watch the land and the people. The Achings have been here forever, and they're not going away anytime soon.