Fin vs. final
The Spanish language, like many languages, has different words to describe the separate concept of 'end'. Two such words are 'fin' and 'final'. Though they share similar bases and meanings, the application and usage of these words can vary significantly.
Fin
'Fin' is a noun that refers to the end or completion of something, either concrete or abstract. It often refers to the last part or conclusion of events, actions, situations or periods of time.
Es el fin del mundo.
(It's the end of the world.)
Hoy marca el fin de nuestra aventura.
(Today marks the end of our adventure.)
Final
'Final' could be either an adjective or a noun. As an adjective, it describes something as being last in a series or progress. As a noun, it refers to the ultimate decisive contest in a sports tournament or competition, or generally refers to the culmination of something.
El final de la película fue muy decepcionante.
(The end of the film was very disappointing.)
Estamos en el partido final del torneo.
(We are in the final match of the tournament.)
Summary
'Fin' and 'final' both carry the notion of 'end' but are used in different contexts. 'Fin' usually denotes termination or completion, whereas 'final', besides also denoting termination or completion can further indicate being last in a series as an adjective and refer to a decisive contest as a noun.