When two particles are entangled, one can measure the properties of one of the particles and instantaneously know the properties of the other. This is because the two particles possess the same properties when entangled, no matter how far apart.
Which properties are entangled?
Is it just fundamental properties, such as spin, or can it be instantaneous/changing properties, such as the speed of the particles?
It may seem very odd to suggest that speed could be entangled, but I think it's a reasonable question to ask as quantum entangles is plenty weird anyway.