CFDs are complex financial instruments and carry a high level of risk due to leverage. A significant proportion of retail investors incur losses when trading leveraged products such as CFDs. You should carefully consider whether you understand how CFDs work and whether you can afford to take the high risk of losing your capital.
Currency appreciation occurs when one currency increases in value relative to another. If yesterday you needed 1.25 USD to buy 1 EUR and today you need 1.35 USD, the euro has appreciated. This movement directly affects traders, importers, and anyone who deals in foreign currencies.