MetaTrader 4 is a trading platform. It offers realtime trading and charting. It can work with custom technical indicators and Expert Advisors.
"As well as many technical indicators and line studies, there is built-in language for trade strategies programming MetaQuotes Language 4 (MQL4). Using this language, you can create
Expert Advisors, Custom Indicators and Scripts.
Expert Advisors can analyze the situation on the market, make decisions, put pending orders, and open positions in on-line mode without trader's participation. Custom Indicators, just like technical ones, can analyze the situation on the market and generate various signals. As for Scripts, they are designed for single execution of some actions."
MetaTrader(MT) is the same. no matter where you download it from. There are many brokers who offer MT. You can download lots of indicators and ExpertAdvisors (EAs) from this forum.
An EA is a program which trades automatically based on the coded rules. You have to download the EA file *.mq4 and put it in your metatrader\experts folder. After that, you must open this *.mq4 file and click "Compile" on top of the MQL editor. This way, your Expert is compiled and should appear on the "Navigator" window of the MT. To make an EA to trade, you have to attach it to a chart. It will use the chart's timeframe and currency pair (usually). You must "allow live trading" in the EA's properties when you attach it. If you get a smiley in the right upper corner of your chart, your EA is working. If that smiley appears like this

, you must enable expert advisors from Tools - Options - Expert Advisors.
I hope you get it. Please search this forum for more info. I'm sure you'll find what you need. You may also visit this link:
http://www.metaquotes.net/terminal
Good Luck!