An order is your command to the broker to, say, "sell 100 shares of AAPL".
An executed order (or partially executed order) is when all (or some) of that command is successfully completed.
A transaction is an actual exchange of shares for money, and there may be one or more transactions per executed order. For example, the broker might perform all of the following 5 transactions in order to do what you asked:
- buy 40 of your shares internally for its own purposes
- sell 5 of your shares to another client who wants to buy them
- send 20 of your shares to an external dark pool
- sell 25 of your shares on the NASDAQ exchange
- sell 10 of your shares on the BATS exchange
On the other hand, if the broker cannot execute your order, then 0 transactions have taken place.
The fee schedule you quote is saying that no matter how many transactions the broker has to perform in order to fill your order -- and no matter what the share prices are -- they're only going to charge you $0.005 per share ($0.50 in this example of 100 shares), subject to certain limits.
However, as it says at the top of the page you linked,
Our Fixed pricing for stocks, ETFs (Exchange Traded Products, or ETPs) and warrants charges a fixed amount per share or a set percent of trade value, and includes all IB commissions, exchange and most regulatory fees with the exception of the transaction fees, which are passed through on all stock sales.
certain transaction fees are passed through to the client. The transaction fee you included above is the SEC fee on sales. Many (but not all) transaction fees DO depend on the prices of the shares involved; as a result they cannot be called "fixed" fees.
For example, if you sell 100 shares of AAPL at $150 each,
SEC fee = $0.0000231 * 100 * 150 = $0.3465
But if you sell 100 shares of AMZN at $940 each,
SEC fee = $0.0000231 * 100 * 940 = $2.1714
So the broker will charge you the same $0.50 on either of those orders, but the SEC will charge you more for the expensive AMZN shares than for the cheaper AAPL shares.
The reason this specific SEC fee mentions
aggregate sales rather than
trade value is because this particular SEC fee applies only to the seller and not to the buyer. So they could have written
aggregate trade value, but they probably wanted to highlight to the reader that the fee is only charged on sells.