What does that mean,when I write border="2" ?What will happen ?

Answer 1

Maybe you could start learning css, it will come handy when you want to style your html codes.
However, it is always the best idea to actually try the code in code playground.

https://www.sololearn.com/learn/CSS/1101/

Also, please remember to use the search bar before posting to avoid duplicates. ✌️