A question about "struct Move

Struct Move
{
// packed storage rep, set in clamp
S32 px, py, pz;
U32 pyaw, ppitch, proll;
F32 x, y, z; // float -1 to 1
F32 yaw, pitch, roll; // 0-2PI
U32 id; // sync'd between server & client - debugging tool.
U32 sendCount;

bool freeLook;
bool trigger[MaxTriggerKeys];

void pack(BitStream *stream);
void unpack(BitStream *stream);
void clamp();
void unclamp();
};

I do not know what the "bool trigger[MaxTriggerKeys]" means,
and who can give me a answer?
THANKS!!! ^_^