What is Beethoven's Symphony No. 5 about?

Although the previous two contributors are not completely wrong, Beethoven himself never actually revealed any programme for the Fifth Symphony. The idea of a fate motif was fabricated by people later on. Like all of his symphonies except the 3rd (Eroica), 6th (Pastoral) and the final movement of the 9th, with its setting of Schiller's 'Ode to Joy', the Fifth is a piece of 'absolute music'. This means music for music's sake without a specific programmatic intention.