Explore the third lecture of MINICOURSE 2 on rational surfaces over a field, part of the AGRA IV (Arithmetic, Groups and Analysis) series. Delve into advanced mathematical concepts presented by renowned speakers Damiano Testa from Warwick, UK, and Tony Varilly-Alvarado from Rice, USA. Gain insights into the intricate world of algebraic geometry and number theory through this 55-minute lecture, which builds upon the foundations laid in previous sessions. Enhance your understanding of rational surfaces and their properties over various fields, contributing to a deeper comprehension of arithmetic geometry.