The Stream summary is like a social media news feed of participant contributions. The Stream will display content in reverse chronological order by default (i.e. Recent Responses). You can choose to orient the Stream based on the available options to cater to your immediate need.
If you'd like to see the actual flow of responses / replies to specific Activity or Discussion Topic in chronological order, use the Oldest Responses option. If you're looking to review socialization surrounding certain responses / replies, use the Recent Comments option.
Use the Stream to quickly review contributions, give feedback (e.g. Like ratings) and ask probing questions via comments. The Stream allows for interesting text snippets to be highlighted, saved and codified as Excerpts.
You can also drill down on any item to see it in greater detail by selecting the View Response option which will take you to that specific Task's response page with Response Options.