What's the difference between Bind and Eval

Data-binding expressions are contained within delimiters and use the Eval and Bind functions. The Eval function is used to define one-way (read-only) binding. The Bind function is used for two-way (updatable) binding. In addition to calling Eval and Bind methods to perform data binding in a data-binding expression, you can call any publicly scoped code within the delimiters to execute that code and return a value during page processing.