Not sure how much help i can be, but the above equation can be used to estimate vapor pressure at a given temperature. generally, it shows the relationship between temperature and vapor pressure. i think the difficult thing to understand about it is when they start talking about 'phases' and 'enthalpy of vaporization', but worry not. in basic terms, this equation is saying 'i have a vapor which at this temperature, is a known pressure. if i add the right amount of energy (the enthalpy of vaporization bit) creating a new temperature, substitute these values in to find the new vapor pressure.
