Is there a difference between dry and granular fertilizers?

No, they are synonymous. Now, there are dry powdered fertilizers that are meant to be dissolved in water, so we don't want to get confused there. But "dry" fertilizer means "granular" fertilizer. These are applied in dry form by mixing with planting soil or sprinkling over the surface of soils. Fertilizers come in many formulations and strengths (almost to a fault). But dry ones can be divided into two groups, quick release and slow release. Quick ones release their elements in days to weeks. Slow ones, in weeks to months.