Salchicha vs. chorizo
The Spanish words 'salchicha' and 'chorizo' both refer to types of sausages, but they are different in their ingredients, preparation methods, taste, and regional usage.
Salchicha
A general term for sausage in Spanish. Usually refers to a fine or coarse grained sausage that can be smoked, boiled, or fried. It's often made from ground meat such as pork, beef or chicken.
Voy a preparar unas salchichas para la cena.
(I'm going to prepare some sausages for dinner.)
Me gusta la salchicha en el desayuno.
(I like sausage for breakfast.)
La salchicha es un ingrediente común en los hot dogs.
(Sausage is a common ingredient in hot dogs.)
Chorizo
A specific type of spicy Spanish sausage. It's typically made from chopped pork and pork fat and seasoned with smoked paprika and other spices. There's also a Mexican version that tends to be softer and spicier.
El chorizo español se cura y se puede comer sin cocinar.
(Spanish chorizo is cured and can be eaten without cooking.)
Voy a añadir chorizo en la paella.
(I'm going to add chorizo into the paella.)
El chorizo mexicano es más suave y picante que el español.
(Mexican chorizo is softer and spicier than the Spanish one.)
Summary
'Salchicha' is a broad term used in Spanish to describe all types of sausages, while 'chorizo' refers to a specific type of Spanish or Mexican sausage, which is usually spicier and has distinct flavors due to the use of spices, particularly smoked paprika.