How can I track a phone using IMEI online without an app?

I’m trying to figure this out too! I lost my daughter’s old phone and someone told me IMEI tracking was a thing, but I’m really confused about how it actually works. Do you have to contact the police first, or can regular people do this? I’m worried about accidentally doing something that’s not allowed. Is it even legal to track IMEI if it’s your own phone?