Genetic drift is referred to as an event of evolution that occurs due to chance.
When genetic drift occurs the frequencies of the alleles change suddenly and purely by chance.
The genetic drift may either lead to loss of some alleles from the population or may cause other alleles to get fixed.
The Founder effect is an example of genetic drift where a small population gets separated from a larger one and a new colony is established from this small population.
In this case, the smaller population is known as the founder population and since these small population will not have the combination of all the alleles that were present in the bigger one, the allele frequencies would change and hence, genetic drift occurs.
