SectionBuffer belongs to the category of PUPs (Potentially Unwanted Programs) that exhibit characteristics of both adware and browser hijackers. The application also is spread among users in the Apple ecosystem predominantly.
No matter what features the particular PUP may boast as having, this category of applications rely on deceptive distribution techniques for proliferation. The most common ones are being packaged alongside another freeware product in a technique called 'bundling' or hiding inside a fake software installer/updater.
SectionBuffer's goal is to start monetizing its presence on the user's computer as soon as possible. It does so by running an intrusive advertising campaign that could significantly reduce the user experience on the affected machine. After all, no one likes being constantly interrupted by unwanted pop-ups, banners, coupons, surveys, etc. Furthermore, clicking on any of the advertisements could represent a security risk as they could take the user to dubious or unsafe third-party websites.
SectionBuffer doubles the annoyance it can cause, however, by also acting as a browser hijacker. The application can take control over the user's Web browser, more specifically over the homepage, new tab page, and the default search engine settings, and force them to open a sponsored address. In the vast majority of cases, the promoted address is that of a fake search engine.
Users also should keep in mind that having PUPs installed on their systems also could mean that their online activities are being monitored and logged. PUPs and browser hijackers are known for collecting information including visited websites, the search history, clicked URLs, and more that will afterward be uploaded to remote servers.
To stay as safe as possible, consider using a professional anti-malware product to clean your Mac from all suspicious PUPs.