as scru mentioned a field aka property, variable or parameter that holds a value or collection of values. You can assign values to and get values from these types of objects.
A method on the otherhand is a piece of executable code. It may return nothing (void) or return a value. Typically you will use a method to cause something to happen such as populate some component on your form, or carry out any number of tasks.
To understand some of these basics, you should grab one of the many wonderful programming books. All programming languages have the basic concepts of storing data in some variable, and calling methods (also called functions and procedures in different languages).