Most of these services offer some form of free portfolio tracking - this enables you to create a portfolio and track it properly to see how you do with no money on the line. This used to be known as paper trading in the 'good old days' before 2001. This kind of exercise can be a good way to learn and play around with things without being either serious or costly.
Trading platforms are portals through which users access and manage their trading accounts for their financial markets. This helps the users maintain their accounts. Generally, such platforms are offered by brokers in exchange of some fee or discounts on trade commissions. With the advent of the discount broking industry, several platforms are also available for free or rather, access to platforms is included in the brokerage you pay. These platforms can be used to conduct research, keep a track of various financial products you wish to trade in, place orders, store your past trade details as well as to authenticate users. Trading platforms have opened up the possibility of e-trading or online trading.