The average is the sum of the chosen statistics in the bootstrapping sample divided by the number of resamples.
Minitab displays two difference values of the chosen statistic, the value of the observed sample and the value of the bootstrap distribution (Average). Both these values are an estimate of the population parameter and will usually be similar. If there is a large difference between these two values, you should increase the sample size of your original sample.
Because the average is based on sample data and not on the entire population, it is unlikely that the average equals the population parameter. To better estimate the population parameter, use the confidence interval.