The phrase "core focus" refers to the main or central area of concentration or attention. It describes the essential or most important aspect that someone or something focuses on. Full definition
Common Core focuses on critical thinking, not only introducing concepts, but also supporting students in becoming more independent in using them, she said. (host.madison.com)
Speaking and listening: Common Core focuses on both aspects of literacy. (indianapublicmedia.org)
I'll be demonstrating upper body and core focused exercises that can either be added to your current routine, or when combined, can be done as a standalone workout. (onnit.com)