The expression "\log_a(b)" represents the logarithm of the number b with base a. It answers the question: "To what power must a be raised to obtain b?" For example, if a is 2 and b is 8, then \log_2(8) equals 3, because 2 raised to the power of 3 equals 8. Logarithms are useful in various fields, including mathematics, science, and engineering, as they help simplify complex calculations, especially when dealing with exponential growth or decay. They also play a crucial role in computer science for analyzing algorithms and data structures.