A mathematical sequence is a list of numbers arranged in a specific order, following a particular rule or pattern. Each number in the sequence is called a term, and the position of each term is usually indicated by its index. For example, in the sequence 2, 4, 6, 8, each term increases by 2, making it an arithmetic sequence. Sequences can be classified into different types, such as arithmetic, geometric, and Fibonacci sequences. An arithmetic sequence has a constant difference between consecutive terms, while a geometric sequence has a constant ratio. The Fibonacci sequence is a famous example where each term is the sum of the two preceding terms.