Yes, the freely available content is restricted to the D&D Basic Rules and D&D System Reference Document.
These rules allow you to play any of the standard races and classes and either DM or play the game of D&D.
You will find that the free rules do not have access to all of the subraces, subclasses and additional content from the source books, such as Forest Gnomes, Drow and Battlemaster Fighters.
If you want access to the expanded content on D&D Beyond, you will need to unlock the content through one time purchases on the Marketplace.