Brønsted-Lowry acid is the any chemical species that acts as a donor of protons while Brønsted-Lowry base is any chemical species that acts as a proton acceptor.
In the following equation: HCOOH(aq) + PO43-(aq) = HCOO-(aq) + HPO42-(aq)
HCOOH is the proton (H+) donor, hence, is the Brønsted-Lowry acid
PO43- is the donor acceptor, hence, is the Brønsted-Lowry base
HCOO- is the conjugate base that forms from the acid
HPO42- is the conjugate acid that forms from the base
