A linear sequence is a list of numbers in which each term is generated by adding a constant value, known as the common difference, to the previous term. For example, in the sequence 2, 4, 6, 8, the common difference is 2, as each number increases by 2. Linear sequences can be represented using a formula, typically in the form of a_n = a_1 + (n - 1)d, where a_n is the nth term, a_1 is the first term, d is the common difference, and n is the term number. This formula helps in finding any term in the sequence efficiently.