Probiotics vs Prebiotics
Probiotics are live microorganisms. Prebiotics are substrates—often particular fibers—that are used by microorganisms and can influence the gut ecosystem.
The simple distinction
Think of probiotics as adding microorganisms and prebiotics as supplying compounds that selected microorganisms can use. The biology is more nuanced, but this distinction is useful.
Food sources
Fermented foods may contain live microorganisms, while many plant foods provide fermentable fibers. Not every fermented food qualifies as a probiotic, and not every fiber is a prebiotic.
Supplements
Products that combine probiotics and prebiotics are often called synbiotics. Their effects depend on the actual ingredients and formulation, not the category name alone.
Which is better?
There is no universal winner. The better choice depends on the intended outcome, evidence, diet, tolerance and health context.