Fresh Content in the eyes of Google isn't just about uniqueness while this is an important factor because if your content isn't unique then its definitely not fresh and more duplicate content.
It's not 100% certain how Google factors fresh content but here's what the SEO scene believe to be close to how Google Factors fresh content into its algorithms.
But to give you an example how fresh content plays out take the following topics into consideration and ask yourself would you rather an old page for the search or aged....
- Things going Viral, Recent News and Events, Current Trends
- Reoccurring Events/News such as Lottery Numbers
- Recurring updates to pages such as reviews
Fresh content means actually what it means... Its Fresh... So if you have a page dated today.. it's fresh, after time it will become aged and not so fresh..... If you have constant people leaving comments on the page then this can be considered fresh, or if you revisit the page and update it week or monthly then it becomes fresh again...
I recommend you take a look at How Fresh Content Can Influence Rankings...