The expression "ab - ac" represents a mathematical operation involving the variables a, b, and c. In this expression, a is a common factor in both terms, allowing for simplification. By factoring out a, the expression can be rewritten as a(b - c), which makes it easier to analyze or solve in various mathematical contexts. This type of expression is often encountered in algebra, where factoring is a key skill. Understanding how to manipulate expressions like "ab - ac" helps in solving equations and simplifying complex problems, making it a fundamental concept in mathematics education.