Codons are an (effectively arbitrary) grouping of 3 consecutive nucleic acid bases that ribosomes can translate into a amino acid when building a protein. Technically any combination of 3 consecutive bases could be considered a codon, however biologists usually only group base pairs based on how they are normally read by a ribosome. Note that this means it is possible for a single sequence of nucleic acids to code for multiple proteins, with the only difference being the starting offset.
Proteins are made of amino acids not nucleic acids. Nucleic acids are polymers whose elements contain a phosphorus group. Amino acids contain an nitrogen group (an amino group to be specific).