When people say Office 365 migration mostly they are talking about exchange migration. It does not include other components of Microsoft 365 like Teams, SharePoint, OneDrive etc. For mailbox or exchange migration there are 4 approaches:

1. Staged Migration - A staged migration moves mailboxes in batches over a period of time. You should use a directory synchronization tool that replicates accounts from your on-premises Active Directory database. At the end of the process, all mailboxes are hosted on Office 365.
2. Cutover Migration - A cutover migration is an immediate migration from your on-premises Exchange system to Office 365. All resources such as mailboxes, contacts, and distribution groups are migrated at once.
3. Hybrid Migration - Office 365 hybrid migration lets you integrate Office 365 with your on-premises Exchange servers and your existing directory service. This allows you to synchronize and manage user accounts in both environments.
4. IMAP (Internet Message Access Protocol) Migration - Internet Message Access Protocol (IMAP) migration lets you migrate users from Gmail or other email systems that support IMAP migration.