Office 365 is the Microsoft Office suite of applications.

Microsoft Office is mobile friendly and offers great tools for collaboration.with better access to critical documents.

Office 365 also supports Microsoft’s vision of cloud computing, specifically that of running a company’s groupware suite of apps. With Exchange Online, SharePoint Online, and Lync Online, users get all the benefits of accessing their email, calendar, company resources, and communication tools without the need of an extensive infrastructure or a big IT department.

Office 365 becomes a subscription service. Like all software as a service (SAAS) offerings, there are various options to choose from depending on your particular needs.

OFFICE 365 FEATURES

The first of these features are the core of Office. To achieve the goal of being able to work whenever and wherever, users can access, create, and edit documents in any of these three ways:

Office applications
The regular Office applications (Word, Excel, PowerPoint, etc.) you know and love, updated to take advantage of the collaboration and cloud file syncing features.

Office Mobile
Native mobile apps available for Windows Phone, iPhone, iPad, and various Android devices.

Office Web Apps
Online versions of Word, Excel, PowerPoint, and OneNote, available on any computer with a web browser.

Both the Office Mobile and Office Web Apps are game changers for Microsoft and they demonstrate their commitment to keep their Office users, regardless of which platform they choose to use.

Connect employees and offer seamless access to insights with Microsoft Office 365

In addition to the standard Office applications available in new ways, Office 365 also offers access to several other services that can make Office 365 more enticing:

One Drive (formerly SkyDrive)
OneDrive is a relatively new product, but it is a core component of the Office 365 suite.  It is the part that takes care of collaboration, file backup, and synchronization features. If you’ve used or heard of Dropbox or Google Drive then you are already familiar with what OneDrive provides but with better integration with Office apps.

Exchange
Outlook/Exchange accounts are hosted in the Microsoft cloud, which means you don’t need to have a dedicated server to run and maintain, and the administration is all done through a web page, which makes the routine IT tasks easy. Email, calendar events, and contacts are all stored remotely, safe and secure inside Microsoft’s data centers.

Lync
Another key component of Office 365, Lync is a communication tool that makes collaboration faster and easier. Users are able to send instant messages, audio and video calls, and share screens and presentations, either one-on-one or to a group of users. If your company leverages services like GoToMeeting or WebEx, then using Lync as part of your Office 365 subscription can replace these types of services and provide some cost savings.  A handy feature of Lync is that it integrates with your Outlook account and automatically updates your status (e.g., when you are in a meeting it will automatically set your status as busy or if you are out of the office it will use your out of office message as its status).

SharePoint Online
SharePoint Online brings its world-class collaboration and information-sharing platform to the cloud. Organizations using older versions of SharePoint on-premises can migrate their content and take advantage of all the new features. One thing to note if you are planning to migrate your old SharePoint solution to SharePoint Online is that custom on-premise solutions may not work or be supported.  This can add significant cost to your migrations.

source – Brian, this is where this text came from, i did fast rewrite
https://www.credera.com/blog/technology-insights/microsoft-solutions/office-365-clear-concise-overview-office-365/