The strength of acids and their conjugate base is inversely proportional - The stronger the acid, the weaker its conjugate base will be. So if you were to compare HCOOH with, say, HCN (pKa ~9.4), CN- is the stronger conjugate base compared to HCOO-. This is because the HCOO- anion is more stable than the CN- anion, so it has less of a drive to retake the proton it donated.
Hope this answers your question.