Could you explain the difference between passive diffusion and facilitated transport?

Passive diffusion occurs without any transmembrane proteins being involved, the molecules cross the lipid bilayer following a concentration gradient (from the highest concentration to the lowest). Small uncharged molecules or hydrophobic ones cross this way (the best example is H2O).

Facilitated transport also involves a concentration gradient, however in this case the molecules cross the cell membrane through specific transmembrane proteins. These facilitate their passage, they are channels for the molecules (e.g. ions, glucose...).