The complexity of a typical ecommerce platform implementation involves various risks during the project. These may lie in the technology stack used, in the connection with back-end systems, in business logic, search, data or all of the mentioned items. Finding and resolving these risks with a full team as you go will endanger the project budget and scope.
During the exploration phase, much is done to investigate these risks, find solutions and decide on going forward. Tackling these with a smal(ler) team at the beginning of the project will help during the engineering phase. The main difference with a full scale functional and technical design is that only risk areas are detailed and that the approach can be more hands-on when needed.
Typically, workshops are held to identify the major risk areas with the team. These can then be investigated, with so-called spikes. Spikes come from Extreme Programming (XP) and are a way to get extra knowledge on the topic, tehnical and/or functional. On scaledagileframework.com, a short and simple guide for doing spikes can be found.