What is tag <b>? What are its use??

Answer 1

It makes a text bold.
https://code.sololearn.com/Wt5rPhDl7PDZ/

Answer 2

<b> makes text bold. Same as <strong>.

Answer 3

Both <b> and <strong> makes the text appear bold, but there is a difference. <strong> indicates an important topic which causes search engines to index the page different. <b> is just text decoration.