These are ‘tit-for-tat’ links. For instance, you make a deal with your friend who has a business website to have him place a link to your website, and in exchange your website links back to his. In the dark ages of SEO, this used to be somewhat effective. But these days, Google considers such 'link exchanges' to be link schemes, and you may get hit with a penalty if you're excessive and obvious about it. This isn't to say that swapping links is always bad, but if your only motive is SEO, then odds are that you shouldn't do it.

Unfortunately, Google has stopped delivering a lot of the information about what people are searching for to analytics providers, but you can use SEM Rush (or similar tools, such as SpyFu) on your own site to get a sense of the terms you’re ranking for and their estimated search volume. Google also makes a bit more of this data available in their free Webmaster Tools interface (if you haven’t set up an account, this is a very valuable SEO tool both for unearthing search query data and for diagnosing various technical SEO issues – more on Webmaster Tools set up here).
Page and Brin founded Google in 1998.[22] Google attracted a loyal following among the growing number of Internet users, who liked its simple design.[23] Off-page factors (such as PageRank and hyperlink analysis) were considered as well as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the kind of manipulation seen in search engines that only considered on-page factors for their rankings. Although PageRank was more difficult to game, webmasters had already developed link building tools and schemes to influence the Inktomi search engine, and these methods proved similarly applicable to gaming PageRank. Many sites focused on exchanging, buying, and selling links, often on a massive scale. Some of these schemes, or link farms, involved the creation of thousands of sites for the sole purpose of link spamming.[24]
SEO means "search engine optimization" and it's a crucial part of your overall online strategy. It’s about improving your online visibility by achieving high rankings on Google search results and attract organic search traffic. There are several SEO services you can buy to help you boost your online presence. These include on-page optimization such as keyword research and meta tags, off-page optimization to enhance online authority with quality content and link building, and technical improvements to help your site achieve more prominence in search results.