Demo account is good to backtest any system gtrading and also new ea, on demo account we will free from emotion pressure but will useful to learn on real market condition, very advisable for newbie they start practice on demo account before start on real account
Basically, new traders should practice their demo, until they are unable to make money in their practice account! But I see, maximum traders are not using the demo account with this manner; so when they go for the live trading, they lose their real money!