The document summarizes a company's migration from their current SharePoint 2010 environment to SharePoint Online. They divided the 3300 sites and subsites into weekly groups to migrate over 29 weeks. They worked with a vendor to perform the migrations using ShareGate. They provided extensive training to prepare users and established communication channels. The migration process involved notifying sites two weeks and one week before their migration, allowing a checkout period, and then locking down the SharePoint 2010 site when complete. Some challenges included dealing with sensitive data and inactive sites. Overall the migration was a success and they have deleted over half the original sites, with the business enjoying the new SharePoint Online environment.