The Microsoft Windows 7 operating system was a popular one, and is still in use by a lot of people. However, it's about to reach end of life.
That means as of January 2020, Microsoft will no longer support or update Windows 7. Why is that bad? Because if hackers find a new bug or flaw in Windows 7 they can use it to deliver viruses/malware, and Microsoft won't fix the issue. Also if you have a problem and need support for Windows 7, you'll be out of luck.
So what to do? You should upgrade to Windows 10 soon, if your computer can handle it. If not, you should think about getting a new PC.