The solubility of a solute is measured as the maximum mass in grams which can be dissolved in 100 g of solvent at any given temperature. At this point, the solution is referred to as being saturated. If any more solute were added to an already saturated solution, it would remain undissolved in the solution.
Solids become more soluble as temperature increases. Warming the solvent helps the solute to dissolve, forming a solution quicker. This is because when the solvent is heated, all of the particles gain energy which causes them to vibrate and move faster. The faster the solute and solvent particles move, the better their chances of interacting with more particles, thus increasing the rate at which they are able to form a solution.
So the temperature (and therefore energy that is put into the situation) will have a big effect on how much of a solute we can dissolve into a solvent, and hence its solubility. That's why solubility gives a value for a specific temperature, as if you increase the temperature the value for solubility will be different.
For example, at a temperature of 20oC the solubility of a solute is approximately 85 g/100 g water, whereas at a temperature of 60oC the solubility increases to 112 g/100 g water.
Let's try some questions on temperature and solubility.