Forex Demo

A Forex demo shows you how Forex Currency Trading works before you start trading with real money.
Before airplane pilots start flying on their own, they have to practice in simulators that re-create what flying will be like without taking any actual risks. Currency trading is as dangerous financially as flying is physically, so it makes sense to trade on demo first, too.
A Forex demo is a good way to start. You can learn the basics by reading books and taking online courses can, but the best way to learn is by getting some hands-on experience. If you start with Forex, hands-on experience could mean losing lots of money, so a demo gives you real-world training with no actual money being involved.
Usually, the demonstration comes courtesy of a brokerage that has an interest in giving you a free demo account. They hope that once you have tested your skills on the demo, you will get into the trading with the real money and you will take advantage of the paid services the demo provider offers, like Forex signals, managed accounts, automated trading, etc.
You should never pay for a demo. There a lots of brokers who offer free demo accounts, so it is absolutely not necessary to pay for it.
When you sign up for a Forex demo, you will be given a username and password and shown how to use the demo system. Sometimes it involves downloading a piece of software unique to the company; other times it is simply done over the Internet. You decide how much imaginary money you want to start with, and off you go!
Forex demo allows you to trade as if it was with real trading. You can read the charts, follow the trends, visit online forums to get other traders' opinions, and make trades. The trades are recorded in the Forex demo only and don't go anywhere into the actual market since there's no real money involved. When the market changes, the program determines how much you'd have gained or lost based on the decisions you made. Once you have gained some expertise using the Forex demo, you can move on to the real thing and start making some real trades.