Take a kettle or a teapot. Add water to it. Boil the water and add tea powder/tea leaves to it based on your choice. The more tea you add, the stronger the liquid becomes. Note that tea is the solute and water is the solvent. Also the tea powder insoluble in water, but the essence is absorbed by the liquid. Once the tea+mixture starts to boil, dissolve sugar (another solute) in it. You may add sugar as long it is soluble in it for maximum sweetness. To this solution, add milk if you need milk tea. Once it is boiled, remove it from the heat source and filter the solution for tea powder. You can see that the residue you get is tea powder, and the filtrate (the liquid after filtration) is black/milk tea.