What is the difference between databinding methods, #EVAL and #BIND

Eval is read-only, whereas Bind is read/write. So if you have a control that updates data (by way of a DataSourceControl), then you should use Bind. If the data is for display only, then use Eval.
The Eval function is used to define one-way (read-only) binding. The Bind function is used for two-way (updatable) binding.