Three noise families, three looks
Perlin noise places pseudo-random gradient vectors on a regular grid and interpolates smoothly between them, giving continuous, organic variation. Simplex, Perlin's later scheme, uses a simplicial lattice with the same goal: less axis-aligned bias and cheaper evaluation in higher dimensions. Film grain is per-pixel random variation, the closest practical approximation to photographic speckle. Low frequencies read as soft blobs; high frequencies as fine texture.