Port, or The Hub, is where you go to choose a level, purchase characters, purchase Red Hats, etc.
Every time a Story Mode level is completed, it will give you two options: "Continue Story," and "Return to Port." This area is accessible when clicking "Return to Port." After finishing a Free Play level you are returned here automatically.
It's appearance resembles Port Royal from the Pirates of the Caribbean Movies.
It starts with a small dock. there are four maps, one for each movie. Each movie map has 5 levels. On each side of the dock, there are building Gold Bricks, which you earn from completing levels, getting all your compass pieces, getting all mini-kits, or getting True Pirate. Once you have enough bricks, you can build them fully, and unlock new locations in the Port level. When you swim/slide across the water in the level hub part of port there are more gold bricks to be built.
In the area across the water from the maps, the town and bayou area through the gate to the left, and the watchtower and pier area past the unlockable gate to the right of the maps you can find Red Hats which unlock extra abilities.
The more areas you unlock earning gold bricks, the more extras you can find. Also these areas are filled with studs, which return every time you return here. So if you're saving up to unlock minifigs of red hats, don't go to the next chapter of Story Mode but instead go here to grab those easy studs.