The text discusses how to use expressions in Aerospike to calculate the value of Pi using a Monte Carlo technique. The Monte Carlo method uses the probability of a random point falling within a circle versus an enclosing square to estimate Pi. The technique is applied in a single Aerospike record, with expressions used to compute whether a point lies within the circle or outside and update counters accordingly. The code example demonstrates how to insert random points and use expressions to calculate the estimated value of Pi, which converges to 3.14xx.