Britannica Online has carefully edited articles on all major topics. It fits the ideal purpose of a reference source as a place to get started-- or to check on as you read and write: articles written by easy-to-identify (or signed) credible authors that give you the most accepted facts and opinions about a topic. Most articles give you links or references to additional research.
Wikipedia is "written collaboratively by volunteers from all around the world" and relies on the collective wisdom of its volunteers to get the facts right and to balance the opinions expressed in the articles. It can be very useful as a starting point for most topics, especially for obscure topics and topics with very special or passing popular interest.
Some Temple University faculty instruct their students not to use Wikipedia as a source because of the volunteer approach to editing, which can be unreliable at times. So, to be safe, use Wikipedia to get started, but move on from Wikipedia to works with an identifiable author from a traditionally edited or published source.