Difference between select is that you can select several objects at once. Objects that are selected are also placed in the Selection object which you can use methods on. Unless you are selecting multiple objects, selecting (say, a cell) activates the object.
Activate just simply makes the object the active object.
Best way to think of it is "many cells can be selected, but only one may be the active cell at any given time."
Note: They both have one thing in common - they are rarely ever needed and they do generally don't do anything but slow your code down. You can work directly on an object without selecting or activating it and it's best practice not to use these unless needed.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…