A FamilySearch blog provides the details. Here is an excerpt:
Mormon Migration Index Give you More Than Ever Before
If you have Mormon ancestors who crossed the ocean to join the Saints in America, you may have heard of the Mormon Migration website. In the past, folks have come to this website to find voyage information about people who made this life changing journey to the Land of Zion. Now this valuable website has been revised to include even more historical information than ever before.
This revised internet site is in the 2nd stage of a 3 stage development plan. This phase provides more images of ship manifests and more articles. This collection of articles will continue to grow with the addition of more than 100 articles in the near future.
Find a Voyage:
Using the Mormon Migration site, you can search through the many personal accounts to discover stories, letters, journal entries, and other accounts for each voyage. Links take you to passenger lists, person accounts written by people who were on board each ship, and scanned images of the ship’s passenger logs. This is a remarkable source for learning not only about your migrant ancestors but also about those who traveled with them and events that took place during each voyage.Share What You Know:
The Mormon Migration database includes thousands of passenger records, stories, journal entries, scanned registry images, and other information, but it is far from complete. It is hoped that users will add information they have about their migrant ancestor. They are especially interested in first-hand accounts of voyages, photographs, and other information.