An ergonomic keyboard is designed for the user's hands to be more naturally spaced rather than forced together in front of them as they are when using a traditional keyboard. The positioning of the keyboard of the keyboard to fit the body is important in order to eliminate discomfort caused by awkward postures.
Some of the ergonomically designed keyboards are split adjustable and some are simply split. Take a look at the features of each to see what will work better for your body.
The Best of the Best section lists my favorite split, adjustable keyboards.