"End up" and "wind up" have the same meaning; examples:
If he does not stop driving under the influence of alcohol, he is going to wind up having an accident.
If you continue to work hard, you might end up with a promotion.
"Grasp" and "understand" are similar, but grasp is only used to refer to understanding an idea or information, and must always be followed by a noun or a grade containing a noun, whereas "understand" can stand alone. However, you can always use "undrstand" if you are not sure.
I listened to her speech, but I did not fully grasp her meaning.
I listened to her speech, but I didn't fully understand her meaning.
I explained it to you in my e-mail; did
Hope this helps!