What is meant by this?
it means you should take action as soon as possible. After April 8, 2014, Microsoft will no longer provide security updates or technical support for Windows XP. Security updates patch vulnerabilities that may be exploited by malware and help keep users and their data safer. PCs running Windows XP after April 8, 2014, should not be considered to be protected, and it is important that you migrate to a current supported operating system – such as Windows 8.1 – so that you can receive regular security updates to protect their computer from malicious attacks.