It's a shellscript that they encrypted. They decrypt it and feed the decrypted output immediately into the shell, to be sourced.

That encrypted secrets file could contain any shellscript, so the aliases are stored in there, together with the API-Keys and passwords.

    source-secret()                                                                                                                                               
    {                                                                                                                                                             
      if [ -z "$1" ]; then                                                                                                                                        
        echo "Need filename to source"                                                                                                                            
      elif ! [ -f "$1" ]; then                                                                                                                                    
        echo "File '$1' does not exist"                                                                                                                           
      elif ! which aescrypt >/dev/null 2>&1; then                                                                                                                 
        echo "Could not find required dependency 'aescrypt'"                                                                                                      
      else                                                                                                                                                        
          . <(aescrypt -d -o - "$1")                                                                                                                              
      fi                                                                                                                                                          
    }