Directional characters are characters such as parentheses, brackets, braces, etc. In LtR text, an "open" bracket is a left bracket, while for RtL text an "open" bracket is a right bracket.
Sometimes (especially in the process of transforming a bidi-unaware application to be bidi-aware), it is useful to have the system automatically "swap" between the symmetric characters. This way, the processing part of an application may be left unchanged, while the presentation part is taken care of by this automatic swap. Note that this automatic swap is relevant only for RtL text (or RtL text segments within LtR text).
For Example (Visual, RtL text).
Storage buffer : (1) hebrew Display : werbeh )1( without symmetric swapping Display : werbeh (1) with symmetric swapping