Thank you! Here are my questions: What is a "platform" and how does it interact with a "broker"? I currently use Scottrade, now can I get a platform like AmiTrade or something and link it to my Scottrade account? How? Thanks again! PS I'm mainly interested in day trading
A "Platform" is your software that you use. In the case of a retail broker like you mentioned, it's the screens and applications you use which they provide. As to whether something will "connect" to your account, that's a question for your broker.
A platform, as it has been mentioned above, is the software that you use to send orders to your broker. Brokers usually provide their own platforms that can only be used to submit orders to them. On the other hand, there are independent platforms (aka multi-broker or broker-neutral) that can connect to a broker of your choice assuming your broker supports this.
Any software that accepts third party plug-ins is a platform. Your web browser is a platform. Notepad is not a platform. http://www.pcmag.com/encyclopedia_term/0,2542,t=platform&i=49362,00.asp