This test does not rely solely on the direct paternal (yDNA) or maternal (mtDNA) lines and is more inclusive in that all can participate and find family. There is a caveat though.
It tests the autosomal dna (atDNA) that we all inherit, randomly, from all of our ancestors. Although there is a random nature to which ancestor's dna survives the inheritance process and although the likelihood of detectable shared dna segments decreases as each generation passes, many are confirming matches beyond the four to six generations advertised as the extent of this test.
Family Tree DNA FAQ 628 shows the probabilities of detecting a match.
So it is rather a lottery, but a useful, and fascinating, addition to the genealogists' toolkit for all that.
Runciman Lineage 1a Lines
Runciman Lineage 1b Lines