From Disney's Hollywood Studios Wiki
Park Icons, in reference to Disney Parks, is a central building or item that is in the park and serves at least one of three purposes, Marketability (used widely in merchandise for the park), Themeing (To catch your attention in the park), and Housing (Having an Attraction, shop, and/or restaurant inside). In all of the Magic Kingdom Parks, it is a Castle (Sleeping Beauty's in Disneyland, Disneyland Resort Paris, and Hong Kong Disneyland, Cinderella's in Walt Disney World Resort, and Tokyo Disneyland) but in the other parks it can be a very different object like Spaceship Earth in Epcot, or the Tree of Life at Disney's Animal Kingdom.
 Studios Reference
Unlike the other Disney parks, Disney's Hollywood
The Chinese Theatre: The Chinese Theatre is located at the end of Hollywood Boulevard and houses the Great Movie Ride. It was the original icon of the park, and early Imagineers always referred to it as the "Castle" of the park. It was planed to serve all three purposes originally, but the Graum's Chinese Theatre in Hollywood, California, which this building was based off of, had copyrights to the likeness of the theatre and would not allow Disney to use the building's likeness in Marketing, causing it to lose two of it's purposes, and only be used for housing.
The Earful Tower: The Earful Tower, which is a giant water tower with Mickey Ears on top, is located as part of the Studio Backlot Tour (one of the few stops to be on every version of the tour) and is based off of a similar water tower at the Walt Disney Studios in Burbank California. There is also a slightly smaller, but very similar tower called the "Earffel Tower" in the Walt Disney Studios Park in Disneyland Resort Paris. Though always planned to be in the park, the Earful Tower took over as the Marketing Icon when the plans for the Chinese Theatre fell through. Most items to have the Disney-MGM Studios name on it had the Water Tower. The Biggest problem with the tower was that, unlike all of the park icons in every other park, this wasn't in the middle of the park, in fact, it is in the very back of the park, so plans were eventually made for a new central icon. However, the Earful Tower
The Sorcerer's Hat: The Sorcerer's Hat is a giant version of Yensid's Hat the Mickey Mouse took in the "Sorcerer's Apprentice" scene in Fantasia. It was added in 2000 as park of the 100 Years of Magic Celebration, Celebrating Walt's 100th Birthday. It is located directly in the Middle of the park, right in front of the Chinese Theatre, completely removing it from possibly being used for Themeing anymore. The Sorcerer's Hat Main purpose is for Marketing, and has since been almost exclusively featured on nearly ever Disney-MGM Studios/Disney's Hollywood Studios Merchandise, however, besides a small pin Store, it houses nothing, and most certainly does not fit in with the 1920-1930's Hollywood theme that Hollywood Boulevard and Sunset Boulevard are known for, nor is it within a theme of an actual Movie Studio.