Answer 1

Non visual tags are those which doesn't display on webpage for eg meta tags.

Also Please use search bar before asking any question in Q/A to reduce duplicate threads.

These link will guide to visual tags and elements regarding your question.

Check these:
https://www.sololearn.com/Discuss/1393286/?ref=app
https://www.sololearn.com/Discuss/43496/?ref=app
https://www.sololearn.com/Discuss/13362/?ref=app
https://www.sololearn.com/Discuss/2064663/?ref=app
https://www.sololearn.com/Discuss/205105/?ref=app
https://www.sololearn.com/Discuss/1822131/?ref=app