Core-Satellite Theory is traditionally known as an investment strategy that incorporates traditional Fixed Income and Equity based securities (i.e. index funds, ETFs, passive mutual funds, etc.) known as the "core" portion of the portfolio, with a percentage of selected individual securities in the Fixed Income and Equity based side of the portfolio known as the "satellite" portion. The Private Banker has made an adaptation of this definition and applied it to intra-day and swing trading. In this adaptation, the term "Core" refers to being the passively managed portion of a position that has an intended larger target while the "satellite" term reflects the actively managed portion of a position that is scaled in and out to add alpha while actively managing risk.
You can learn more about the Core-Satellite Theory approach in our Trading Education.