Difference between dew point and boiling point?

Boiling point is the temperature(at a particular pressure) of a pure substance at which it boils . e.g water at 1 atm will boil at 100 degreeC. If u start heating water

its temperature will rise from ambient to 100 degC only until it totally boils to steam.

For a mixture of two components there will not be a single b.p. During boiling its temp will rise so the mixture will have an initial b.p and a final b.p.

For a pure component you only have boiling point, if u cool steam from say 120 degC, water will condense out at 100 degC.

If you cool air which contains water which we call water vap or moisture, the water will condense at a particular temp which we call as dew point. This temp will depend on the amount of water vap in the air.