What is the difference between HTML tags <a></a> and <a href=""></a>?

Question

Some websites use [url]website address[/url] in their text area and cannot add anchor text there, can someone explain this to me? I'm confused about this [url][/url]. I know how html anchor tag works but not the second one. Thanks

I tried googling and couldn't find any solution, hope someone can explain it to me

Answer 1

is the HTML tag

[url] is the BBCode tag.

They are used in different contexts.

https://en.wikipedia.org/wiki/BBCode

Answer 2

is an HTML tag and [url] is a BBCode tag.

HTML is a core web technology that can be rendered by any web browser; BBCode is more limited in scope and is used by some websites to allow a limited safe subset of HTML Functionality, which does not allow users to do things they are not supposed to do (such as running scripts or messing with website styling).