Advertising spending is one of those ambiguous areas of supply and demand theory where we don't really know exactly what will happen but we can make a pretty good guess. Our first guess would be that advertising affects consumer's tastes and preferences in a positive way, and that this will result in an increase in demand (the demand curve will shift up/right). But advertising also costs firms money. The distinction we have to keep in mind is whether or not advertising affects the marginal cost of production, or whether their advertising budget is fixed. The difference between these two methods decides whether or not the supply curve will shift.
But first let's focus on shifting of the demand curve. Imagine that there is a product that you are not familiar with, or that you do not have enough information about to justify purchasing it. For this example, we can think of computers. So maybe you go to a computer trade show and start looking around. At these trade shows, you will see many trade show displays that contain information about products. This information/advertising, if done correctly, will make you desire to purchase the product. This means that you are experiencing a change in your tastes and preferences (in a positive way), and this results in an increase in demand.
So if advertising does not affect marginal cost, then we know for sure that equilibrium price and quantity will both rise (look at the first graph on the right, with only demand changing). This is because only demand shifts, and since it increases we have more people buying the product which increases quantity demanded, and because firms are only willing to supply the increased amount at increased prices, the price goes up as well. However, if both supply and demand shift, then we know for sure that equilibrium price will go up, but the answer for quantity is ambiguous. Look at the graph below to see what I mean: