The significant figure of a value or measurement is the number of important digits that it contains
The main purpose for learning about significant figures in science and/or technology courses is precision of measurements.
In science and technology experiments and reseaches, we always want to ensure that measured values are as close to the true values as possible. This is because any deviation from the true value can invalidate the result of the experiment. Also, errors due to repeated approximations can have cummulative effects on the experimental results.
Therefore, the knowledge of significant figures is useful in science and technology to be able to record values of experimental measurements as close as possible to the actual value.