Abacus, the ancient calculator, is introduced as a tool for fast calculations. The focus begins with the school abacus suitable for beginners, featuring ten rods and 100 beads representing place values from one to billion. Preschoolers can learn counting by moving beads corresponding to numbers or patterns like '1 more,' counting in increments of 10s (e.g., 10-20), or smaller steps such as by 5s and 2s. These activities make learning interactive and adaptable based on age.