By web definition: Contextual advertising is a form of targeted advertising for advertisements appearing on websites or other media, such as content. It is a form of targeted advertising for advertisements appearing on websites or other media, such as content displayed in mobile browsers. It relates directly to the content of the webpage on which it is served.
Example: If you are sending any sms to your known ones from a free sms sending website like “I got promoted today” then the ad under the text sms may come as “kuch mitha ho jaye (Let’s have some sweet” an ad served by Cadbury. Another example is if the user is viewing a website pertaining to sports and that website uses contextual advertising, the user may see advertisements for sports-related companies, Adidas, Reebok or Nike’s product.