Okay, imagine there's a big group of people, and they all have different hair colors. Some have blond hair, some have brown hair, some have black hair, and some have red hair.
Now, let's look at just one gene that affects hair color. This gene has different possible versions, called alleles. For example, there could be an allele for blond hair, an allele for brown hair, and so on.
The allele frequency spectrum is like a way of counting how many people have each allele in our group. So, let's say we count up all the alleles for hair color in our group. We might find that 30% of the alleles are for blond hair, 40% are for brown hair, 20% are for black hair, and 10% are for red hair.
This is the allele frequency spectrum for our group's hair color gene. It tells us how common each allele is in the group. Scientists study allele frequency spectra to learn things about genetics, evolution, and how populations change over time.