HSERIN & HSEROUT automatically use the PIC's hardware USART pins. Which pins these are can be found in your datasheet.

Most serial LCD's require inverted data format. The hardware USART uses non-inverted, since data will normally pass through a MAX232 level converter.

If you use the hardware USART to communicate with your serial LCD, and your LCD requires inverted data, then, with HSEROUT, you'll need a TTL level converter, or use one of the other serial commands like SEROUT, SEROUT2, or DEBUG.

These commands allow you to control whether the data is inverted or non-inverted, and use just about any I/O-pin. HSEROUT does not.