There are 3 sections in reports tab: Category Reports, Brand Reports, Excel Reports. Your Excel exports from product page will be listed here, please be informed you can only see the last 5 excel reports that you generated. Daily excel reports sent by email will not appear here. 

Category and Brand reports will give you a summary of the products. You can see the index value of the Brand or the Category with your overall position, cheapest competitor including you and most matched competitor for the brand or category. There is also a pie chart which shows your positions.  

The videos below are explaining reports page in detail and export function.