A solute is a substance that is "dissolved into" the solvent, while the solvent is the substance "into which" something is dissolved. Now, when we prepare sugar water, we mix sugar into water and thus sugar is the solute, while water is the solvent. The solvent is generally the bulk phase, which is water in this case. Thus, for sugar water:
Similarly, when we mix salt into the water to make some brine solution, salt is the solute, while water is the solvent.
While preparing solutions, we can alter the rate of the dissolution of solutes by increasing their surface area (using crushed sugar instead of sugar cubes) and by stirring the solution. We can also increase the solubility of a particular solute into solvent by increasing the temperature of the solvent.
Hope this helps.