This is Stefan Keil's talk "What is ... a Diophantine equation?" at the "What is ...?" seminar. The talk was given on Friday, January 14, 2011, 12:45pm at the BMS Loft at Urania.
As a warmup to Professor Funke's lecture, we introduce Diophantine equations and present a famous example of how elliptic curves can be employed in their solution: namely, Fermat's Last Theorem.
For more "What is ...?" seminar videos, visit math.fu-berlin.de/w/Math/WhatIsSeminar.