Search engine marketing, also known as SEM is a form of online marketing which involves buying your spot in the search engine results pages. When you choose a keyword or a set of keywords you want your site to appear for, you have to bid against your competitors. The highest bids win a spot, either on top of organic results or on the right side of the screen. You only pay when somebody clicks your ad, therefore if you get displayed but you don’t get visitors, your exposure is free. However, you want people to click because the purpose of SEM is to attract visitors to your website.
The best known search engine marketing program are Google AdWords and Yahoo Search Marketing. Both programs are free to join and they don’t have any minimum budget limits, so you can spend only as much as you can afford and you can pause your campaigns whenever you need. This is great for situations like those when you are low on stock and you don’t want to have too many people place orders until you manage to replenish it.