From the Introduction:
Beginner's Essentials provides just the essential information and tables a beginning player needs to create and play first level characters. This booklet does not provide all of the information necessary to run a Basic Fantasy adventure or campaign, and Game Masters should have a copy of the Basic Fantasy Role-Playing Game Core Rules which contains an introduction to role-playing, many more details about the game, and full descriptions of the various classes, races, equipment, etc. Players whose characters have reached second level will also need to consult the Core Rules. Additionally, I recommend Simone Felli's BFRPG Charts and Tables as a useful reference, especially for GMs. Both can be downloaded for free from basicfantasy.org.
Please note: References to the Core Rules include page numbers taken from the 2nd Edition, Release 75 version of the rulebook. If you have an earlier or later copy of the rules, the page numbers may be incorrect.