HTML Elements

Upto HTML 4.01. block level elements and inline elements. 

inline elements: 

• respect l to r margins and padding. not top and bottom
• cannot have width and height set
• allow other elements to sit to their l and r
• can display things before and after it, on the same line.
• span, a, strong, em, img, input, abbr, acronym

block

• respect all of those
• force a line break after the block element
• demands its own line with whitespace around it. 
• <p>, <div>, h1 to h6, ul, ol, dl, li, dt, dl, table, pre, form

From HTML5 onwards

https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Content_categories

Talking about attributes, you can use data-* attributes to store extra information on standard semantic HTML elements. (link)

HTML5 WAI-ARIA is a spec defining support for accessible web apps. (link, link)

Difference between aria and data attributes

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