Definition of <source> HTML Tag
Basically, The <source> html tag is used to specify multiple media resources for media elements, like <video>, <audio>, and <picture>.
The <source> tag allows you to specify alternative video/audio/image files that the browser may choose from, based on its media type, codec support, or media query.
Definition of SRC attribute
When <source> is used in <audio>, <video>, and <picture> OR <img />. That time the SCR attribute required to specifies the URL of the media file.
Syntax Example Of <source> and SRC attribute
<source> tag is used in <audio> tag with SRC attribute
<audio controls>
<source src="URL_audio" type="audio/ogg">
<source src="URL_audio" type="audio/mpeg">
</audio>
SRC attribute is used in <img /> tag
<img src="Image_URL" alt="image description" title="image title description" />