The first is the market value of your current property. That's the amount your home will likely sell for in today's market. When you know its market value, you'll have a better idea of how much money will be available to invest in a new home.
The second is an overview of what's available on the market. Which of the homes currently available for sale meet your criteria with respect to the type of home, its special features (such as a big kitchen or pool), the neighbourhood, etc? How much are these homes selling for?
With those two pieces of information, you'll be able to make a better decision.