On Salesforce Records

Every record has a Currency field that specifies the currency type for amounts in that record. All currency amounts display in the record’s currency and are also converted to the personal currency of the record owner, based on the conversion rates entered by your administrator. Amounts in the user’s personal currency are displayed in parentheses.
For example, if you do business with Acme, Inc., a German company, you can set the Currency field in the Acme, Inc. account to “EUR - Euro.” Amounts such as Annual Revenue will display in euros as well as in your personal currency.
You can set the Currency field for a record to any of your organization’s active currencies. If a particular currency is deactivated and it is already in use as a record currency, those records remain untouched. You cannot enter any new amounts using an
inactive currency