In English, 'dog' and 'cat' and 'you' are three-letter words that mean different things. Those scientists call a three-nucleotide 'word' a 'codon'. Ya see, code is part of the word codon. With 4 different nucleotide 'letters', you can make 64 different three-nucleotide 'words'. There are only 20 different amino acids, so 64 'words' are more that enough to tell the ribosome what to do.
Lets make our own message using three-letter English words.
If we made this chain, someone would read the message and tell each person or animal where to get in line. As each one got in the right order, the reader would tell them to hold hands, or paws, to keep them in the right order. The ribosome does it slightly differently. The ribosome needs help with the reading part. It gets that help from my cousins, the transfer-RNAs.