What does * mean?

Question

Came across this codes... have no idea what does the * mean... any idea??

Example1: byte * ptr = (byte *) imageData.Scan0.ToPointer( );

                   byte * ovr = (byte *) ovrData.Scan0.ToPointer( );

 

Example2: v = (int) *ptr + (int) *ovr;

                   *ptr = ( v > 255 ) ? (byte) 255 : (byte) v;