BasicTransaction is the name of a piece of adware that affects Mac computers.
BasicTransaction is one member of a family of dozens of virtually identical pieces of Mac adware, believed to be part of the AdLoad family. They all share the same app icon - a generic grey circle with a white looking glass icon in it. They also share more or less the same functionality - they act like most ad-supported software, pushing intrusive ads on the target system they are installed on.
BasicTransaction will cause ads to appear, both embedded and as pop-ups, if you have it installed on your system. The ads don't only cause longer page loading times, they can also expose the user to further online threats.
A lot of the time, the ads displayed by adware are sourced from rogue advertising networks. This means those ads can link to misleading websites, untrustworthy pages and questionable content. The presence of adware on your system is never desirable and the general recommendation is to remove any adware you are aware of as quickly as possible.