Windows 10 brought back the very familiar styling of the Windows 7 Start Menu and melded it with elements of the Windows 8/8.1 Start Screen.
Prior to the November Update for Windows 10 you could customize it and choose to either hide or show your most used and recently added apps on the new Start Menu.
These settings are located at Settings > Personalization > Start.
The November Update to Windows 10 now brings another option for customizing your Start Menu and that is to show app suggestions.
A feature like this is intended to help with app discovery but if you want to keep a cleaner, more streamlined Start Menu then you can turn this feature off.
To turn this on and off just open up to the Settings > Personalization > Start page and click the Occasionally show suggestions in Start.