Binance.order_limit_buy

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

order_limit_buy(symbol, quantity, price, time_in_force \\ "GTC")

Creates a new limit buy order

Symbol can be a binance symbol in the form of "ETHBTC" or %Binance.TradePair{}.

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