Which one do I use

I fall asleep and cannot understand alllllllllllllllll this talking, so will someone help me:

I copy from laptop to extern HD
When I start Sync I want it to check if changes have been made on my laptop: If a file has been erased on my laptop, I want Sync to erase the same file on my extern HD. If I have changed a file on my laptop, I want Sync to copy it to laptop, overwriting the file there.
If I have created a new file on the laptop, I want Sync to copy it to the laptop.
So which option to I choose?
Thanks