Windows 8 users are used to having their Windows login account linked to a Microsoft one (hotmail, live, etc.) but this will become an expectation for Win7 migrators as well. You don't have to - there will be a little link to have a traditional "local" account and can always convert it later.
The new Start Menu will include "live tiles" from Win8's Start screen which can be great for live weather, news, or sports scores.
You'll get the Windows Store and be able to install its apps ... or not, it's not mandatory. You can, for example, install either the Skype app or "Skype for Desktop". Your call.
Win10 will have a Settings App and the classic Control Panel. If you can't find a setting in one, look in the other; especially where it involves user accounts and so on.
A Win8 feature that will carry forward is the option is the ability to Refresh or Reset your Windows installation. The former will install a clean version of Windows (removing any software you've installed) but leave your documents intact; the latter will wipe everything and give you a clean install of Windows.
Microsoft "Edge" will replace "Internet Explorer".
Cortana will be Microsoft's equivalent of Apple's "Siri" for voice search.