Binance.create_order

You're seeing just the function create_order, go back to Binance module for more information.
Link to this function

create_order(symbol, side, type, quantity, price \\ nil, time_in_force \\ nil, new_client_order_id \\ nil, stop_price \\ nil, iceberg_quantity \\ nil, receiving_window \\ 1000, timestamp \\ nil)

Creates a new order on binance

Returns {:ok, %{}} or {:error, reason}.

In the case of a error on binance, for example with invalid parameters, {:error, {:binance_error, %{code: code, msg: msg}}} will be returned.

Please read https://www.binance.com/restapipub.html#user-content-account-endpoints to understand all the parameters