Many consider “broker” and “trading platform” to be the same thing, but they are in fact slightly different.
A trading platform is the software that allows a trader to put buy and sell orders on the market. A broker is the company that facilitates the actual access to the markets and carrying out those orders.
A broker may offer multiple different trading platforms to its clients, for example an in-house proprietary software along with support for the popular MetaTrader 4 independent software platform.
This allows traders to pick the one they like best, and in the case of some independent platforms like MetaTrader, to trade via multiple different brokers on the same platform.