The EU Transaction Log (EUTL) records all transfers of allowances in the EU Emissions Trading system (EUETS). In this short note we provide an introduction into transactions under the EUETS. We first provide an overview how allowance transfers work and who are the involved parties. We then explain the characteristics of these transfers and how the evolve over time. Finally, some Frequently Asked Questions are provided that should lower the barrier of stepping into the analysis of the transaction data.