Img HTML elements belongs to the group of the “self-closing” HTML elements: it means that they do not follow the ordinary structure - open tag, put content, close tag - but they have just one tag which works as opening and closing tag:
As all opening tag it still can receive attributes though, and these are the tools you can use to manipulate the tag, put some content in, enhance accessibility, etc.
The main attributes of an img tag are src and alt:
Attributes are key value pairs inserted into the tag. The syntax is
<tag key1="value1" key2="value2"> </tag> or, in case of self-closing tags,
<tag key1="value1" key2="value2" /> - notice that the pairs are separated by a space character, not by a comma.
<img src="insert URL of the image" alt="Cute dog smiling">