With binary options you usually have a selection of four different trading assets to choose from: stocks, foreign exchange pairs, indices and commodities.
The main reason that so many different asset types are offered is simply because different traders prefer to trade different assets according to what their field of expertise is and what they feel comfortable in trading.
While all brokers offer all the asset types, different brokers offer a different selection of each asset, and also a different amount altogether. Of all the brokers that we currently know of, after reading a Topoption review, we can say that they currently have the largest selection, with around 180 assets in total.
When choosing a broker, it is usually important to take a quick look at what assets they have on offer. Some brokers try to attract more Forex traders by offering more foreign exchange pairs, while others may want to lure in stock market traders by offering more stocks and idices. At the end of the day however, the most important thing is the stability and reputation of the broker you choose.