Some jurisdictions, for example, the US, require you to provide a basis, something like a legal reason, for filing the application. This could be a "use in commerce" or "intent-to-use" basis. There are different legal requirements for each one.
For registering with a "use in commerce" basis, you need to use your trademark in commerce and sell your products or offer your services to US customers. For example, you might be using your trademark in Poland, but until these products are available for purchase in at least one US state (for example, by an option to order it there and pay in USD), this trademark would not be considered as used in commerce.
"Intent to use" basis means that you have not started using your trademark in commerce yet, but you have bona fide intent to do so within the following 3-4 years.
You can read more in our article Intent to use versus use in commerce (US).