ELI5: Explain Like I'm 5

how to make bold text in html

To make bold text in HTML you need to use <strong> tags. <strong> tags tell the web browser that the text should be bold. When you want to make other pieces of text bold, you just need to wrap it in the <strong> tags. For example, if you want to make the text "Hello World" bold you would write it like this:
<strong>Hello World</strong>