What is capital?

The word capital is another word for money; or the machines, tools, and buildings used in the production of goods and services

"A capital" can be a capital letter (upper case).

"A capital" is also a city that is the seat of government for a nation or state, or sometimes smaller government divisions.

A+man-made goods used in the process of producing other goods

Capital is any monetary wealth (cash, stocks, loans, etc.) or machines (computers, assembly-line machines, lawnmowers, etc.) used to produce goods and services. This is contrasted with labor, which is any human input to the production of good and services.
To run any kind of business activity, you'll need things. These things aren't the same as B2B, truly include equipment, tools, equipment for your office, automobiles, computer systems, etc. These assets are bought with cash. Cash is usually known as capital.