“A blog is a discussion or informational website published on the World Wide Web consisting of discrete, often informal diary-style text entries. Posts are typically displayed in reverse chronological order, so that the most recent post appears first, at the top of the web page.”
Blog websites loosely follow a standard format where the entries are all stored together as an archive in date order with (as Wikipedia says) the newest on top. However, the layout and style of presentation can vary considerably. Some are accompanied by photos or sketches, some can have sound and others can consist of a video created by the author (the “blogger”).
These last ones are called Video Blogs or, more commonly, Vlogs and the authors known as “vloggers”. At one time they used to be called Vodcasts (video) - the counterpart to Podcasts (audio) - but this term has now largely been overtaken by Vlogs. To confuse you further, the majority of vlogs these days are uploaded to YouTube and vloggers who regularly post to YouTube create their own YouTube Channel. There is money to be made out of these channels. Here is a brief example of a vlog www.youtube.com/watch?v=Jvmapd07hPc
Leaving video aside, the common form of a blog is the written page. Bloggers usually draw attention to their writings by posting about them on social media like Twitter, Facebook and so on. Other bloggers operate a regular newsletter which is sent out by email automatically (daily, weekly, monthly or at irregular periodic intervals) to all those people who “follow” or “subscribe to” the bloggers’ writings. The email usually consists of a brief summary of the blog article and a link to the full version on the blogger’s website.
Bloggers often use an email contact list of subscribers. It is best practice only to include names and email addresses on this contact list at the expressed request of an individual. Those subscribers retain the right to have their details removed (to unsubscribe) at any time. Many blogs invite comments or questions and all contributions will be stored on the website alongside each blog entry. Like other social media these comments can often lead to a protracted debate (worse still an argument) among the subscribers. The better blog websites will quickly step in and prohibit such discussion.
Unscrupulous people can often create email contact lists without an individual’s knowledge when an email will take the unsuspecting user to (at best) a sales and marketing website or (at worst) a malicious destination. There is big money made by people in selling email lists which are then used to send out these emails to unsuspecting users. This is the origin of SPAM emails and similar hazards.