To interpolate means to estimate between two known numbers.
example, suppose a girl’s height was 152 cm on 1st January
last year and 156 cm on 1st January this year. A reasonable
estimate of her height on 1st July halfway through last year
is 154 cm.
using the simple function to calculate new data points we
usually do not receive the same result as when using the original
function, but depending on the problem domain and the interpolation
method used the gain in simplicity might offset the error.