Deceptive Advertising
Many ways of deceptive advertising are in use. Several of these are illegal, though punishments are almost non-existent.
Bait and Switch
If you came to a store because of an advertisement that stated a handsomely low price, and the product isn't there, you can suspect being manipulated with the "Bait and Switch" method. When you are then guided towards a similar, but more expensive product, you can be sure of that. The "bait" is the first, attractively priced product, and then you are "switched" to the product that they wanted to sell to you in the first place.
In many countries, the Bait and Switch method is illegal.
Hiding important information
Sometimes there is important information about a product, that you as a consumer need to know. When a product is bad for your health, or addictive, like tobacco, you do need to know. Deliberately hiding such information, as the tobacco industry has been shown to do, is deceptive.