Do you have a link? What I've seen in most discussions is obscuring of the fact that the majority of "capital" is directly or indirectly retirees or people saving for retirement. Those in the top 5% wealthiest often need to survive on that wealth for decades so it's not as if they have per year spending power that is that high. You too will be at your top percentile wealthiest of your life when you are nearing retirement.
Honestly? Your favorite LLM will be able to build you a syllabus better tailored to fit your current level of understanding. But in short, Capital is the people making decisions about how money is expressed through the economy.
But to make concrete what I am saying. Take a VC fund like Lightspeed that manages tens of billions of dollars. They do this on behalf of LPs, of which the largest are typically large pools of long-term capital like university endowments and pension funds.
Lightspeed, for example, has received ~$400m in investments from CalPERS (retirement program for some California public employees) alone. That represents tens of thousands of employees and former employees. Even if the notional value of one of their retirements is (say) $2m, that person is still Labor. Capital is represented by the people at CalPERS who decide where to allocate money, and by the Lightspeed GPs who decide which startups to fund. A former county attorney who has money in CalPERS has essentially no say over how her retirement funds are invested (if she's on a pension); that decision is down to a relative handful of people she will likely never meet.
A quick way to know the difference: top 5% wealthy people can buy the house next door and make it ugly, being a small nuisance. Capital can crash the entire economy with bad bets or get laws changed/ignored at their behest (we are watching this right now with X's CSAM generation on demand).
