substance is something which has an exsting distinct property,
In general terms solution is a mixture in which one substance is solublised in other substance termed as solute and solvent respectively.
it can be of three types depending on the size of the solute particles
True Solution is a homogeneous mixture of two or more substances in which substance dissolved (solute) in solvent has the particle size of less than 10-9 m or 1 nm. Simple solution of sugar in water is an example of true solution. Particles of true solution cannot be filtered through filter paper and are not visible to naked eye.
Colloidal Solution is a heterogeneous mixture in which particle size of substance is intermediate of true solution and suspension.
Smoke from a fire is example of colloidal system in which tiny particles of solid float in air. Just like true solutions, Colloidal particles are small enough and cannot be seen through naked eye.They easily pass through filter paper. But colloidal particles are big enough to be blocked by parchment paper or animal membrane.