Fiat = Traditional, government issued money. Examples include the US Dollar, British Pound, and Indian Rupee. Fiat money has no intrinsic value of it’s own; rather it’s ‘value’ is derived from the public’s perception of the issuing government’s political and economic stability.
Converting fiat currency to cryptocurrency (or crypto to fiat) can be challenging. Laws vary significantly between legal jurisdictions and often change as the crypto-economy develops. One option is to use the services of an Exchange such as Coinbase.