what's liability ?

Other's claims to the business's good stuff. Amounts the business owes to others. 
Usually one of a business's biggest liabilities (hopefully they are not past due) is to suppliers where a business has bought goods and services and charged them. This is similar to us going out and buying a TV and charging it on our credit card. Our credit card bill is a liability. Another good personal example is a home mortgage. Very few people actually own their own home. The bank has a claim against the home which is called a mortgage. This mortgage is another example of a personal liability. Some examples of business liabilities are accounts payable, notes payable, and mortgages payable.