The Y-DNA SNP tests are used for deep ancestry testing. The test looks at regions on the Y chromosome known as SNPs or single nucleotide polymorphisms.
We each have 22 autosome pairs and 2 sex chromosomes. Females inherit two X chromosomes and males inherit an X chromosome and a Y chromosome.
The Y-DNA SNP test looks at only the Y chromosome so can only be tested in men and traces patrilineal ancestry.