what is asset?
what is liability?
well,it depends on the angle from which you are looking at it.
bank deposits are liabilities to the bank because it is other peoples money but it generates income for the bank while bank loans to customers are assets to the bank and it takes money from the bank to generate income in the nearest future.
so the defination depends on the context in which it is used.
Cheexy has given you the Financial Success definition of the meaning of "Assets" and "Liabilities".
This definition will make you financially successful. The other definition given here is that of an Accountant, and that will not lead you anywhere.
For example the house you have on mortgage is not an asset, it is a Liability because it takes money out of your pocket every month.
Follow Cheexy's definition, you are bound to stay the course of financial freedom.