Broker
The firm giving you market access. Quality ranges from excellent to outright scam.
Good broker = tier-1 regulated + tight spreads + reliable execution + fast withdrawals + segregated funds. A broker that takes 14 days to process a withdrawal is telling you something.
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Learn to actually use Broker.
Definitions are the easy part. The free first five modules put this on a real chart and make you do the work. No card required.