How can I check DPI in my phone?

I'm curious, how exactly does one go about checking the DPI, or dots per inch, on their phone? Is this a setting that's accessible through the phone's native operating system, or is it something that requires downloading a third-party app? And if it's the latter, could you recommend a trustworthy and reliable one? I'm not very tech-savvy, so a step-by-step guide would be greatly appreciated. Additionally, I'm wondering if there's a specific reason why someone might want to know their phone's DPI, or if it's just a matter of curiosity.