Having a different description meta tag for each page helps both users and Google, especially in searches where users may bring up multiple pages on your domain (for example, searches using the site: operator). If your site has thousands or even millions of pages, hand-crafting description meta tags probably isn't feasible. In this case, you could automatically generate description meta tags based on each page's content.
When would this be useful? If your site has a blog with public commenting turned on, links within those comments could pass your reputation to pages that you may not be comfortable vouching for. Blog comment areas on pages are highly susceptible to comment spam. Nofollowing these user-added links ensures that you're not giving your page's hard-earned reputation to a spammy site.
In the 1990s, the term Digital Marketing was first coined,. With the debut of server/client architecture and the popularity of personal computers, the Customer Relationship Management (CRM) applications became a significant part of marketing technology. Fierce competition forced vendors to include more service into their software, for example, marketing, sales and service applications. Marketers were also able to own huge online customer data by eCRM software after the Internet was born. Companies could update the data of customer needs and obtain the priorities of their experience. This led to the first clickable banner ad being going live in 1994, which was the "You Will" campaign by AT&T and over the first four months of it going live, 44% of all people who saw it clicked on the ad.