An asset class is a category of thing you can take a position on. What you choose changes your trading hours, your costs, how fast price moves, and how much capital you need.
Forex
Foreign exchange, meaning one currency measured against another. Written as pairs: EUR/USD, GBP/JPY, AUD/USD.
A pair is a single price. EUR/USD at 1.0850 means one euro buys 1.0850 US dollars. Go long EUR/USD and you are betting the euro strengthens against the dollar. You are always long one currency and short the other simultaneously, which is why pairs are quoted this way.
- Hours: around 24 hours from Monday morning in Asia to Friday evening in New York
- Costs: generally the lowest, especially on major pairs
- Common instruments: EUR/USD, GBP/USD, USD/JPY, AUD/USD
Indices
A stock index measures the combined value of a basket of companies. The S&P 500 tracks 500 large US companies, the NASDAQ 100 tracks 100 large technology-weighted companies, the ASX 200 tracks the largest Australian listings.
An index is a number rather than a thing, so you cannot buy one directly. You trade a derivative on it, either a CFD or a futures contract.
- Hours: futures on major indices trade nearly 24 hours, with activity concentrated around the relevant cash market open
- Costs: moderate
- Common instruments: S&P 500, NASDAQ 100, Dow Jones, DAX, FTSE 100
Commodities
Physical goods and resources. Gold, silver, crude oil, natural gas, wheat, copper.
- Hours: vary by contract, generally long sessions with gaps
- Costs: moderate to high, and some instruments move violently
- Common instruments: gold (XAU/USD as a CFD, GC as a future), crude oil (WTI, Brent), natural gas
Cryptocurrency
Bitcoin, Ethereum and others, traded either directly on a crypto exchange or as a derivative through a broker.
- Hours: genuinely 24 hours, seven days
- Costs: usually the highest, and the price gap between venues can be wide
Shares
Individual company stock, such as Apple or BHP. For day trading, usually traded as CFDs if the provider offers them.
- Hours: limited to the exchange session, typically six to seven hours
- Costs: usually commission-based
How to choose as a beginner
Pick one instrument and learn it properly before adding another. Markets have different personalities, meaning typical daily range, typical speed, and behaviour around news. Sampling ten of them teaches you none of that.
Beginners starting with CFDs usually begin with a forex pair like EUR/USD or Gold (XAU/USD) while those who start with futures begin with indices like NASDAQ (NQ).