Owners equity, often just called equity, represents the value of the assets that the owner can lay claim to.
In other words:
It's the value of all the assets after deducting the value of assets needed to pay liabilities (debts).
In the diagram above, the assets amount to $60,000, but the value of the assets the owner can lay claim to is only $40,000. This is because there are liabilities (debts) of $20,000, so $20,000 of the assets will be needed at some point to pay off these debts.
In the simplest terms, owners equity is:
The value of the assets that the owner really owns.