Simplifying expressions involves reducing mathematical expressions to their simplest form. This process often includes combining like terms, which are terms that have the same variable raised to the same power. For example, in the expression 3x + 5x, you can combine the like terms to get 8x. Another technique in simplifying expressions is applying the distributive property, which allows you to multiply a single term by each term inside parentheses. For instance, in the expression 2(3 + 4), you can distribute 2 to both 3 and 4 to simplify it to 6 + 8, which equals 14.