Et al. comes from the Latin phrase meaning "and others." The abbreviation is commonly used in scientific and scholarly writing to stand in for two or more author names.
We use it to indicate and signify that more authors contributed to the original paper than are listed. The authors that are listed are the authors that we worked with to review the additional annotations and educational materials.
As you can see from the list below, almost all scientific papers are a result of collaborations among many scientists—often among many scientific fields, disciplines, and/or institutions.