We currently have our Active Directory running on a Windows Server 2016 machine. It seems to be working out well for us. If I were to use Azure AD, does that run along side my AD on Server 2016 or would I remove the AD on Server 2016 and only run it on Azure AD. We currently use Office 365 for email, OneDrive, Flow, etc. Thanks for advice and suggestions.
Azure AD is in no way a replacement for "traditional" AD, make sure you do your research before committing to getting rid of AD. If you are using Office 365 already, you are already using Azure AD, but if you need more than just the O365 suite, chances are you have to stick with AD.
Hello Azure AD is not a replacement for AD. It's an identity management platform for Microsofts Azure cloud. You can configure a hybrid identity model by using AAD Connect to sync users from your on premises AD to Azure AD. This will allow your organization to take advantage of features like SSO to sign into the different workloads mentioned in your post with same username and password.