Deals are sometimes known as precedent transactions.
For the purpose of your case competition, deals are typically mergers or acquisition and your research will likely focus on finding target (acquired) companies that are typically comparable to the target company of interest. The transaction value (including the take-over premium) can then be used to help value a company under consideration as a target.
Use FactSet and Bloomberg to research a single deal or multiple deals involving public companies. This guide will focus on FactSet but Bloomberg also offers the MA function for deal research.