"understand the purpose of a trust, "
Any number of reasons - protect assets for a minor or someone with a disability/ anonymity.
"let’s say I wanted to pass my home to my nephew in my will, am i free to put a time limit on that? "
You can do anything you like so long as you are unmarried/not in a civil partnership, without children of your own .
" I have worded my will to state my nephew will inherit said house three years after I pass away "
Is there any reason for this? As above, you can do anything you like.................BUT why are you controlling from the grave/afterworld/void?
mf