Internet working but no wireless signal/ network connection showing as activated -how is this possible? Old macbook I use for working in my shed - probably not relevant...

Internet working but no wireless signal/ network connection showing as activated I'm wondering how is this possible? This is an old macbook I use for working in my shed - probably not relevant- and this has started to happen on and off over recent weeks. I'm not complaining as I am very glad I have a connection somehow but I am curious to understand how this happens? Thanks to anyone who can enlighten me.