What is founder effect?

(N/A) Five factors are known to affect $Hardy-Weinberg$ equilibrium: gene migration or gene flow,genetic drift,mutation,genetic recombination,and natural selection.
When a section of a population migrates to a new location,the gene frequencies change in both the original and the new population.
New genes or alleles are added to the new population and are lost from the original population.
If this gene migration happens multiple times,it results in gene flow.
If the change in allele frequency occurs by chance,it is called genetic drift.
Sometimes,the change in allele frequency in the new sample of the population is so significant that they evolve into a different species.
The original drifted population that establishes this new colony is known as the founders,and this phenomenon is called the $founder \ effect$.