Parallax is a cutting edge scrolling technique that gives viewers the feeling they are looking at a two- or three-dimensional website instead of a one-dimensional page.
In short, the effect creations an illusion of depth, drawing viewers into a story or taking them on an adventure.
One of the main benefits of using parallax design for a website is that it allows the site to essentially walk a visitor through a story, just by scrolling down the page.
The ability to tell a story on these sites encourages visitors to scroll through the entire site by sparking their curiosity, often resulting in longer page visits (that’s the “Time on Site” metric in Google Analytics). Although many of these sites are visually outstanding, most parallax websites are considered very unfavorable for search engine optimization (SEO). They often have longer load times, especially if they have numerous images. Because many parallax sites are single-page, there is only the opportunity to specify one Page Title, Meta Description, URL, etc. It’s also difficult to use various keywords on one page of a site. Another con to single page sites is that it prohibits internal page linking within the website.