TRISX(X= any port like A,B etc) is used for define output or input port.0 is define for output and 1 for define input.In your code LCD is connected with portB and you want to send some data to LCD for display purpose so it is define as output port.LATX(X = any port like A,B etc.) is output latch onto which value are written.SPBRG is used for set the baud rate for serial communication.It is all configuration register which is need to be configure as per your application.