Can someone explain the difference between acute and sub-acute?

Have read up on treatment options for shin splints and it says to do certain things in the acute phase and others in the sub-acute phase (but not to do them in the acute phase etc). Does the acute phase basically mean when it's still hurting and sub-acute mean without pain, or is there more to it than that?

Thanks in advance

Acute is immediately after the injury. Subacute is once the injury has started repairing (probably 72 hours onwards or something like that).

If I sustained my injury months ago and the lingering pain returns- that's acute I guess then? I'm gonna give em a rest from stretching/strengthening/foam rolling for a few days at least cos they're mega sore. 

Injury/pain and their meaning.

1. No pain or discomfort, before, during and after training. Ideal.

2. You can feel the injury soon after starting a run and it disapears when you stop. This is usually the sign of a repair mechanism at work.

3. You can feel the injury getting worse when running but having stopped, gradually subsides to almost nothing until the next session when it starts getting worse earlier. This is an overuse injury letting you know.

4. You can feel the injury 24/7. This is known generally as chronic. Time for a rest.

5. Enjoy your stay in hospital.