When sugar is dissolved in iced tea, the solvent is the iced tea itself, and the solute is the sugar. The solvent is the substance that dissolves the solute, while the solute is the substance that gets dissolved.
You would become aware that the solution is saturated when no more sugar can dissolve in the iced tea. At this point, any additional sugar added will remain undissolved at the bottom of the glass. This indicates that the solution has reached its maximum capacity for dissolving sugar at that particular temperature.