Residue

The water passes through the paper and collects as the filtrate; the sand stays on the paper as the residue. This works because the insoluble solid cannot pass through the filter paper with the liquid. It would not separate dissolved salt from water: both pass through.

Water passes through as the filtrate, while sand stays on the paper as the residue. The holes in the paper do not trap dissolved substances, so filtration would not separate salt from salt water.

The paper traps the insoluble sand, called the residue. The water passes through as the filtrate. If the sand is the product you want, wash it on the filter paper to remove solution clinging to it, then dry it.

The solid left on the paper is the residue, and the liquid collected below is the filtrate. Filtering sandy salt water therefore leaves sand as the residue and salt solution as the filtrate—not pure water.