The HTML5 <summary> tag is used by the HTML author to be able to provide heading for the <detail> element. Supposedly, the HTML5 <summary> tag is clickable for the user of the web page. However, this is only applicable for Google Chrome. Other web browsers like Internet Explorer, Safari, Opera and Firefox, have no support for HTML5 <summary> tag.
It has to be remembered that the HTML5 <summary> tag has to be the first child element of the <details> element. The HTML <summary> tag is a new addition in HTML5. For the Event Attributes and Global Attributes, using the HTML5 <summary> tag is easy because it provides support for those attributes.