Google updates its search algorithm on a continual basis in order to improve the customer/searcher's experience, i.e. how close to precisely what they were searching for are the top results?

They trying to improve the relevance of search results. The final goal is creating of AI that understands the meaning of your query, not just looking for some words in text.

Panda filters the low-quality (duplicated and re-writed) content. Pinguin fights with link spam and filters low quality links.

According to my knowledge Google Panda is related to stolen contents and Google Penguin update is related to link spamming.