What is the purpose of using strong and em tags in html?

[GhabriRungtu]

I would like to understand the purpose of using strong and em tags in HTML. Throughout my career, I believed that these tags help blind individuals to better comprehend the websites I develop. However, when I recently began mentoring others, I decided to verify how screen readers actually interpret these tags. To my surprise, neither the Windows built-in screen reader nor NVDA made any noticeable changes in intonation when encountering strong, em, b, or i tags. This has made me echatrandom chatrandom curious about the true significance of using these tags. Could you please shed some light on this matter?