According to volume, forex is considered to be the largest market around the globe. The daily transaction here is around 3 trillion dollars. The volume is created by large institutions and organizations, having different intentions of each.
If you are considering player-wise, then central banks are the giants, like Federal Bank of States, having an intention to control the stability of the nation. Mainly they do trading to maintain country's economic stability and also to sustain foreign currencies, if sometime need arises.
Again Commercial Banks are also deeply rooted parts here. They carry trades by others. According to clients demand they do the exchange. Also for their own speculation and income. Though commercial banks control the most money around the globe, they are the gigantic players for the forex market.
Another crucial portion is covered by the importers and exporters. Since they work with clients of different countries. They also do a locking the market to avoid the variation in the currency rate. They do it to fix their profit ratios.
Finally speculators, like individual citizen, funds, small organizations are also involved in the market. Though they have no intention or support on stabilizing economy, rather they trade for extra income only. But also these trades are done by commercial banks.
