Assets = Liabilities + Equity

This equation is the identity of financial accounting.  At any given instant, it's true.  It's just a snapshot.

Financial accounting requires the economic entity assumption. Our assets are our resources.  This stuff makes up the firm -  it's not mine; it's not yours; it's not even ours.

It's theirs'.  We meet the cast of characters to the right of the equals sign.  They are outsiders of the firm, but they claim all the firm's resources.

The liabilities belong to the creditors.  Creditors are conservative.  Their obligations are determined with certainty.  It's in the contract.  They don't like the firm taking chances when that may hurt the firm's chances of paying them.  Creditors can also be mean.  They can force the firm to liquidate if the liabilities exceed the assets and the firm can't pay their obligations when they come due.  Their claims come first.

The equity is what's left over for the owners.  The owners see opportunity.  They share in the growth of the firm and have an indefinite claim to resources as long as they continue to be owners.  Why own? The firm pays its owners lease payments called dividends for providing them capital.  Investors can be flighty, though.  Investors expect the equity of the firm to grow.  A rational investor who does not expect growth will sell his shares.