Capital is surplus labor that has already been produced by wage laborers and extracted by Capital Owners. Capital owners then use the capital created by labor to extract more Capital via various financial instruments which exist to extract the value created by labor. Making it a cyclical loop growing more and more capital resulting in the vast wealth that Billionaires, corporations, and hedge funds possess today.
Gotcha, here goes. Labor creates value. Capital owners pay labor a fraction of the value they create then hold on to the surplus value which was created by labor that has already been completed. Capitalists then use that 'dead labor' to suck up more value from 'living labor' that they are currently extracting surplus value from. Similar to a vampire sucking blood from living creatures, using the power it already sucked from a creature it killed from sucking blood from.