The trademark system is a use based system such that to have any rights use must be made of a mark in commerce in connection with the sale of goods or services.  For goods , such as products, widgets and things you can touch, this use must be directly on the goods via an engraving marking, label or other direct contact of the marks on the goods.

For services, the rules are a bit more relaxed such that an advertisement using the mark offering the services for sale is usually enough. 

The use requirement is good for businesses in that once use of a mark begins rights begin to accrue at least in the geographic area of such use-even if little thought is put into the mark before use. 

A better plan than just beginning to use a mark  is to think about it first.  When launching a product or business, smart businesses' thoughts also turn to "what are we going to call" the business and/ or the product.  The analysis of what name, logo or combination serves business objectives  should be followed by a trademark search and opinion as to whether or not a new trademark can be safely used.  This search should give the business owner a good idea of whether or not a mark or similar mark is already being used for the same or similar products or services.  This information allows one to determine whether another is likely to object to the use of a new trademark, along with whether the mark can be registered by the Treademark Office. 

This being said there are many examples of businesses that have not thought about what to call a product or have not done a search and are content to deal with the consequences.  Examples include Apple and Tesla, both of whom likely know better but are willing to deal with the consequences. 

Following the creation and search process we come back to whether or the mark has already been or soon will be used in commerce, that is with the sale of goods or services.   

Federal trademark registration is desirable for most businesses that operate across state lines-much more common even for small businesses in the internet era.  Registration provides constructive use throughout the fifty states, provides procedural advantages and can be used as a basis for international applications. 

As indicated, trademark rights accrue based on use in commerce and such use must be proven in applications for trademark registration. Use must be proven when the application is filed or this may be delayed until after approval of the trademark by the trademark office.  

This latter option -delaying proof of use by filing an Intent to Use trademark application- is most useful early in product development cycle.  Such an application can be filed, and approved by the trademark office, but proof of use may be delayed until up to three years from approval by the Office.    

So use of a trademark in commerce in connection with the sale of goods or services is required for the registration of a  trademark by the US Patent &'Trademark Office but such use may be delayed