Nobody really knows what the Google algorithms really are, but we do have a general idea about what each of them looks out for. Here’s a short guide to the Panda and Penguin algorithms to help you to understand more.
Panda: The main focus of the Panda algorithm is to get websites to look at their backlinks and content. Backlinks should be good quality, with no spammy or irrelevant links to your site. Content needs to be unique, as the Panda update looks for duplication across your site and the web. Google also likes your site to have a low bounce rate (the rate at which people stay on the site. A bounce rate of 90% means lots of people look briefly at your site then leave. A bounce rate of 10% is much better as it shows people are staying on your site much longer).
Penguin: Penguin was introduced initally in 2012 and has recently had a fresh update. This one looks more keyword stuffing, unnatural links and dubious link aquisition such as buying links or guest posts. To avoid a penguin penalty, you should get rid of spammy links and focus on natural keyword placement as well as natural anchor text.