Generally speaking, adware is a program that installs an additional component that feeds advertising to your computer, often by delivering pop-up ads or by installing a toolbar in your browser.
Some adware may hijack your browser start or search pages, redirecting you to sites other than intended. Unless you're a fan of guerrilla marketing, such tactics can be annoying. Worse, the mechanism that feeds the advertising can introduce system anomalies or incompatibilities that cause problems with other programs and can even disrupt the functioning of the operating system.
Spyware surreptitiously monitors your computer and internet use. Some of the worst examples of spyware include keyloggers who record keystrokes or screenshots, sending them to remote attackers who hope to glean user IDs, passwords, credit card numbers, and other sensitive information.
Most often, though, spyware takes a more benign but still quite offensive form. The information gathered, often referred to as "traffic data," can consist of monitoring the websites visited, ads clicked, and time spent on certain sites. But even in its more benign form, the collected data can morph into something far more insidious.
Hope this helped.. ;D
