LVP stands for Low Voltage Programming. If that pin is set to Vdd by resistor you can program pic with low voltage on mclr pin (for example 5V) instead regular 13V.
It's an option. If enabled, pin RB3 will be used for LV programming. This pin will no longer be available for normal I/O use.
For details, see page 102 of the datasheet (document DS30221B).