what is elevation of boiling point and depression of freezing point

Boiling-point elevation describes the phenomenon that the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent.This happens whenever a non-volatile solute, such as a salt, is added to a pure solvent, such as water.

In sum, The boiling-point elevation means that when a solute is dissolved in a solvent, the boiling point of the resulting solution is higher than that of the pure solvent. 

ΔT_b = T_{b (solution)} - T_{b (pure solvent)} = K_b * b_B * i

[Where : K_{b =}   RT_b²M/ΔH_v, where R is the gas constant, and T_b is the boiling temperature of the pure solvent [in K], M is the molar mass of the solvent, and ΔH_v is the heat of vaporization per mole of the solvent]

Freezing-point depression describes the process in which adding a solute to a solvent decreases the freezing point of the solvent. 

ΔT_F = T_{F (solution)} - T_{F (pure solvent)} = K_F * b * i 

[Where : K_{F =} The cryoscopic constant, which is dependent on the properties of the solvent, not the solute. Note: When conducting experiments, a higher K_F value makes it easier to observe larger drops in the freezing point. For water, K_F = 1.853 C°·kg/mol.

Boiling-point elevation describes the phenomenon that the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent.This happens whenever a non-volatile solute, such as a salt, is added to a pure solvent, such as water.

In sum, The boiling-point elevation means that when a solute is dissolved in a solvent, the boiling point of the resulting solution is higher than that of the pure solvent. 

ΔT_b = T_{b (solution)} - T_{b (pure solvent)} = K_b * b_B * i

[Where : K_{b =}   RT_b²M/ΔH_v, where R is the gas constant, and T_b is the boiling temperature of the pure solvent [in K], M is the molar mass of the solvent, and ΔH_v is the heat of vaporization per mole of the solvent]

Freezing-point depression describes the process in which adding a solute to a solvent decreases the freezing point of the solvent.

ΔT_F = T_{F (solution)} - T_{F (pure solvent)} = K_F * b * i 

[Where : K_{F =} The cryoscopic constant, which is dependent on the properties of the solvent, not the solute. Note: When conducting experiments, a higher K_F value makes it easier to observe larger drops in the freezing point. For water, K_F = 1.853 C°·kg/mol.