Image that you have a coloring book and a crayon. There is nothing stopping you from coloring outside the lines if you are careless. There might be nothing outside the line so it's no big deal, or there might be something outside the line that you accidently colored over and ruined. That is NOT memory safe.
Now image that you have a stencil. You have a different stencil for every object on the page, and it's clipped to the page. Even if you try, you cannot color over any other objects. That is memory safe.
Image that you have a coloring book and a crayon. There is nothing stopping you from coloring outside the lines if you are careless. There might be nothing outside the line so it's no big deal, or there might be something outside the line that you accidently colored over and ruined. That is NOT memory safe.
Now image that you have a stencil. You have a different stencil for every object on the page, and it's clipped to the page. Even if you try, you cannot color over any other objects. That is memory safe.
This is actually a really great metaphor for buffer overflow! I like it a lot!