Capital Structure is said to be unaffected by the debt here. Is it true?

"A mix of a company's long-term debt, specific short-term debt, common equity and preferred equity. The capital structure is how a firm finances its overall operations and growth by using different sources of funds."
This is what CS is defined in investopedia. So which one is true. please refer to video Capitalization Structure in course "Investment Banking and Financial Modelling" for my question. TIA