Can I buy Wi-Fi for my phone?

Excuse me, I was wondering if you could clarify something for me. I've heard about the concept of purchasing Wi-Fi for personal devices like smartphones, but I'm a bit unsure about how it works. Is it possible to actually buy Wi-Fi specifically for my phone, or is it more of a service that's typically provided by internet providers and accessed through routers and hotspots? I'm trying to understand the best way to ensure I have reliable internet access on my phone, whether it's through a dedicated plan or some other method. Thank you for your help.