@ Lexi:
To my knowledge, the most widely used platform by brokers and retail traders is Metatrader, either Metatrader 4 (MT4) or Metatrader 5 (MT5). There are indeed brokers who create their own platforms, such as Agea broker which offers the Streamster platform alongside Metatrader.
The difference between platforms lies in their features, especially in order placement and the indicators that can be used. For example, the technical indicators on the Streamster platform at Agea broker are fewer than on Metatrader, but Streamster has a chat column that makes it easier for traders to communicate with the broker. In terms of price movements between platforms, there are differences, but they are not too significant.