Its fairly straightforward. There is 'money' and there is 'stock'.
Money funds day to day operations, pays salaries, power bills etc.
Stock determines ownership, and in most corporations governance.
Now day to day you spend money and ideally you also get revenue. If the revenue that comes in for any given month/quarter is more than the money going out that month/quarter then you are 'operationally cash flow positive' meaning that other than something like a big lawsuit or a promissory note coming due or some big financial event you can keep working and the lights on. It doesn't necessarily mean you can hire anyone or 'grow' or fund a PR campaign.
Then there is stock which represents ownership in the company, there can be multiple classes of stock which convey different rights, and there can be corporate bylaws which change how decisions are made while private vs public, but for the simple case we'll assume that 1 to 1, one share of stock is worth 1/(total-stock) of the company and exerts an equivalent amount of control. When you make a decision for the company you at the board level you effectively 'vote your stock' when you vote. If 50.1% of the stock votes one way that is the way the decision goes.
So lets consider a couple of scenarios:
Lets say the Company is :
1,000,000 shares
Investor A - 10% stock (100,000 shares)
Investor B - 15% stock (150,000 shares)
Investor C - 15% stock (150,000 shares)
Founder A - 25% stock (250,000 shares)
Founder B - 25% stock (250,000 shares)
(everyone else in the company) - 10% remaining stock.
Now the two founders, if they agree they can get their decisions ratified by the board with one additional investor voting with them. The 'value' of the company is price-per-share * total shares. So lets say this company was valued at $10M so each share is 'worth' $10.
Now you need more money (revenues aren't covering it) so you try to sell more stock which is going to change the numbers around. Lets say you need $10M for the next 24 months and none of the investors want to invest any more money. You've got a crisis. But if you are also independently wealthy you can say "I'll put in the $10M but I'll take 2 million shares." So the 'totals' after that transaction are 3 million shares in total (up from 1 million) and as a strict percentage we've got:
3,000,000 shares
Investor A - 3.3% stock (100,000 shares)
Investor B - 5% stock (150,000 shares)
Investor C - 5% stock (150,000 shares)
Founder A - 8.3% stock (250,000 shares)
Founder B - 75% stock (2,250,000 shares)
(everyone else in the company) - 3.3% remaining stock.
Founder B now has 'sole control' because they have enough stock to make any decision, vote their own stock, and have that decision be ratified.