All Office 365 Suites include Yammer. I have detailed the benefits of utilising Yammer in a business here:
The Business of Yammer
However, one of the point of confusion for many people is when do you use Yammer and when do you use SharePoint? My guidance is that you in fact use both. Although Yammer can be used to store documents, you shouldn’t. Instead you use SharePoint to hold all the documents with all the benefits it provides and then you use Yammer to have conversations around the documents.
I have detailed how you can have Yammer conversations around SharePoint documents here:
Delve should be the centre of your Office 365 universe
Yet another way to improve the integration between Yammer and SharePoint Online is to embed a Yammer group into a SharePoint Team Site.
I’ve detailed the process in the above video but here is also the written process.

In this case, I’m going to replace the default SharePoint newsfeed you see on the page above with a Yammer group feed.

The first thing to note is that you can’t use this process to embed the ‘All Company’ or home feed from Yammer, you can only do this with a Yammer group.
Thus, in the above example I navigate to my Yammer group (called Learning Office 365) as shown above.

In the lower right hand corner of the Yammer group (you may need to scroll to the bottom of the page) you should find the section Access Options as shown above. In this area you will find a link Embed This Feed in Your Site which you need to select.

Doing so will immediately open a new dialog that contains a snippet of code. Copy this using Ctrl-C.

Now return to your SharePoint Team Site and the page into which you wish to embed Yammer. Edit the page by typically selecting the Edit icon in the upper right corner as shown above.

This will place the page into edit mode as seen above. You should be able to see the page regions and any existing web parts.

To delete the Newsfeed web part simply select the down arrow in the top right corner of the web part to reveal the above menu. From this menu select Delete.

Ensure that the cursor is in the correct location on the page where you want the Yammer feed to appear. Then select the Insert tab at the top of the page. From the Ribbon Menu that appears select the Web Part button.

This will open a window directly below as shown above. In the Categories section at the left select Media and Content. That should display a number of different items in the Parts section to the right. In the parts section locate and select Script Editor.
Select the Add button on the right to complete the insertion process.

You should now see a Script Editor web part in the location where your cursor was on the page. Go to the top right of this web part and select the down arrow to reveal the above menu. From the menu select the Edit Web Part option.

That will display a standard web part editing pane on the right of the screen but it will also display the EDIT SNIPPET option in the web part as shown above which you need to select.

This will now open a new dialog like that shown above. Simply select the box and paste the code you have previously copied using Ctrl-V.

Immediately after pasting the code the dialog will expand and appear like the above. Simply select the Insert button to save the changes.

With the page edits complete, return to the top right of the page and select the Save icon to return to normal page mode.

Once the page refreshes, you should now see the Yammer feed for the group embedded in the SharePoint Team Site as shown above.

You should also see that the conversation is exactly the same as it appears in Yammer.

If anyone now posts an update in the embedded feed, as shown above, it will appear both in SharePoint

and Yammer as you can see above.
Thus, embedding Yammer groups directly into SharePoint Online Team Site means users only have one location to visit to collaborate on a topic. They can of course still interact directly with Yammer if they choose but having the option makes it more likely that will become better engaged with both Yammer and SharePoint Online.