Apex is a computer language that is like some of the more well-known languages including Java and C#. It is different because it has dots and curly brackets in their language. This allows the computer user to develop software programming which must be made with a computer language. Static methods are used in Java when there is no objective stated or listed.
In Salesforce, the class would be considered to be global due to using the web service called SOAP. If you are wanting to request and use a payload format in Salesforce so that it can be received by a static method in a global Apex class and that it uses the web service keyword, it would have to be SOAP/XMIL.