When you need to update Sitecore v7.2 or above to the latest release, the Express Migration Tool helps to automate the process of installing the intermediate versions. This reduces the complexity of bringing an older site up to the latest version.

It is documented here: https://dev.sitecore.net/Downloads/Express_Migration_Tool.aspx

When you need to update Sitecore v7.2/6.6 (or any supported version of the migration tool) to the latest release, the Express Migration Tool helps to speed up the upgrade process by migrating the data to a latest version instance. This reduces the complexity of bringing an older site up to the latest version.

It is documented here: https://dev.sitecore.net/Downloads/Express_Migration_Tool.aspx

When you need to update Sitecore v7.2 or above to the latest release, the Express Migration Tool helps to automate the process of installing the intermediate versions. This reduces the complexity of bringing an older site up to the latest version.

It is documented here: https://dev.sitecore.net/Downloads/Express_Migration_Tool.aspx