Capital, in economics, is any produced asset used to create goods or services machinery, tools, buildings, technology, even skills (human capital). It's distinct from money: money is a medium of exchange, while capital is a productive resource you deploy to generate output or income. Cash sitting in a bank isn't capital until it's invested into something productive.
Businesses use capital in production (equipment, infrastructure) and investment (expanding capacity, R&D) to raise productivity and output over time. At the macro level, capital accumulation more/better tools per worker — is a core driver of long-run economic growth.