By clicking on "Home" on the top banner of any CA Communities page, you will be brought to the page that contains activity streams, following streams and custom streams. The options you will see on this page are News, Top & Trending, Most Recent, Following, and then any custom streams you have created.
The two activity streams (Top & Trending and Most Recent) are automatically generated streams that allow users to get a closer and more detailed look at what's going on throughout the entire CA Communities site. The Top & Trending stream will show you all of the most popular content throughout the communities - including content that has lots of views, likes, or shares. The Most Recent stream will show you the newest updates from the entire communities site, so you can follow along with community activity in real-time.
The following stream is another stream that will appear on the News page by default. This stream works just like the Connections Stream on the previous site, and will be the default option when you choose to follow a person, place or piece of content. Generally, this stream will serve as an aggregate of everything you've followed on the communities, so you have one place to look to see updates on everything you've followed - but it can be used a number of ways! It's up to you how you'd like to utilize this default stream.
Custom streams do not automatically appear on the News page unless you create them. You can use custom streams to organize the content you are following into groups that make the most sense for you. Custom streams can be used as simply an activity feed that you can check up on periodically, or they can be used to generate notifications if you chose to turn mobile or email alerts on. For more information about Custom Streams, check out this doc: Creating Custom Streams.