What to know about BTC
Bitcoin is the first and largest cryptocurrency (since 2009), with a supply cap of 21 million coins. When buying, the rate is only part of the story: the withdrawal fee to your own wallet is a fixed amount of BTC, so on small purchases it can eat several percent. Some exchanges let you withdraw via the Lightning Network, which is usually cheaper. For large purchases order book depth matters more than the fee, because a big order eats through ever more expensive offers.