Go to the main dashboard, and you can find the sentiment listed under each mention:
Positive: Mentions that are good for your brand reputation.
Negative: Mentions that are bad for your brand reputation.
Neutral: Mentions that are a mixed bag of good and bad - balanced mentions.
Unknown: Mentions in different languages or symbols.
You can filter the sentiments here:
If you want to check the Sentiment Summary for your keyword, visit the Reporting Dashboard.