Definitions 
Equity is the remaining interest in an asset after all liabilities are paid. The term "equity" is used in various situations:
The equity in a house for example is calculated by subtracting any loans secured against the house from the value of house. If a house is currently worth $100,000 and has a $30,000 secured against, the owners equity with respect to the house is $70,000.
Business Equity
The equity in a company is the value of it's assets minus it's liabilities. If we imagine a supermarket, owners equity would be ASSETS (real estate: the supermarket building(s) themselves, receivables: funds owed by customers, stock: the products on the shelves, cash: in the tills and held with the bank, etc..) – LIABILITIES (debt: money owed to lenders, accounts payable: money due to suppliers, etc..).
Equity and Business Valuations
It is worth noting that the valuation of a business is not just the equity in the company. Much depends on intangible assets (not necessarily on the balance sheet) such as brand, customer base and customer loyalty. In the end, a valuation is based on the expected cash flow from business activities.
