Yes, Magento has native Review module. It is not so powerful as PowerReviews, but it’s free.
Magento Review module is working simply like a comments to a product.
It doesn’t send emails to a customer after he bought a product.
You can see some reports in Admin area for reviews and reviewed products.
The module is enabled by default, so you can test its functionality, for example, on Magento Community Edition for free.