After all, it could be literally anything.
It could just be an old friend trying to get in touch with you, or an important call from work.
It could even be someone your spouse is potentially cheating on you with, and any number of things in between.
Sometimes people try to call phone numbers back directly, but that's not always the best idea.
If you're looking for another way to find out more, one option you might consider is employing a reverse phone look up service.
A quick internet search might point you in the direction of some of the more popular services, both free and paid, but jumping off the deep end with a paid phone service you might not be that familiar with is just as bad as calling strange phone numbers.
You definitely don't want to start paying for a service that isn't going to be able to help you, so of course it's worth your time to look into which ones are the most informative.
The primary advantage that a paid reverse phone look up service is likely to have over a free one is that the paid services will cover cell phone customers, which aren't otherwise publicly available.
Granted, most of these types of sites aren't extremely expensive to use, but it's your money, and you deserve the right to spend it wisely.
With a little bit of forethought, you can quickly empower yourself.
You'll never need to wonder about the identity of people that call your house again.