The map of Kapalua Airport is basically a map of West Maui. Use this map to get a sense of the Island. Maui is generally divided into 4 population sections. The sections include Central Maui, South Maui, Upcountry and West Maui. Yes, there are more people, but this where where the bulk of the population reside. The resort areas tend to be in South and West. The best swim and snorkel beaches are also in South Maui and West Maui.
Notice that West Maui lodging generally has ocean views of Molokai Island and Lanai Island.
West Maui has some of the best resorts and beach. Some of the resort hotels include: The Ritz Carlton, Hyatt, Marriott, Sheraton, and Westin. There are lots of other choices for accommodations. In addition to the high end resorts you'll find plenty of rental condos, smaller resorts, time share rentals and vacation rentals. For an overview of hotels on the west side of Maui try searching Hotel In Hawaii. For car rentals we recommend Maui Car Rental.
West Maui addresses can be confusing. There is only one post office. The Lahaina post office, so you may notice that wherever you stay on the west side there is a Lahaina city address. For example, Kaanapali, Kapalua, Napali, etc. are all Lahaina address. The US Post Office for all these towns is the same.