Assets - Liabiilities = Shareholders' Equity or simply Equity
What this means is that whatever assets that a company owns, subtracting whatever the company owes, gives you what's left for shareholders. This is also known as the book value of the company.
Shareholders' Equity is usually at the bottom right of the balance sheet (Assets on the left side, Liabilities on the top right) and is usually broken down into the following sub components:
Paid in capital
Others: there are actually a lot more complicated stuff but I will just lump it under others and we will talk about that on another day.
Common stock and paid in capital are usually thought of as the original capital of the company. Common stock is the no. of outstanding shares multiplied by its par value which is usually some arbitrary no. like $1 and paid in capital is usually the proceeds received during IPO or subsequent secondary equity financing.
Retained earnings would be the impt sub-segment to know. Needless to say, retained earnings comes from net profit (from the P&L statement). So what this means is that retained earnings should be as big as possible. If you see a company that has an original capital of say $1mn but retained earnings is like $80mn or some big no. then you know this co. has created tons of value for shareholders. And conversely, if paid in capital is bigger than retained earnings, either this firm is still very young, or it has continously raised new money from shareholders ie old shareholders keep getting their stake diluted and the business model's sustainability is questionable
Preferred stock is basically a stock pays dividend forever and is usually not a big sub-segment. Thus it pays to find out why a co. might have a huge preferred stock capital.
Treasury stock is a negative entry (ie the $ amt here is negative not positive) in shareholders' equity and it arises only when a company does share buybacks. This is a good sign bcos it signifies that the company has its shareholders in mind and is using share buyback as a way to return capital to its shareholders.