When visiting Amsterdam, you don't want to get these two terms mixed up. They may mean basically the same thing in North America, but they are two vary different places in Amsterdam.
A cafe serves alcohol, and might be called a pub or a bar elsewhere.
On the other hand, a coffee shop is an Amsterdam specialty that sells coffee as well as marijuana and hashish. You certainly don't have to buy or use any drugs while you at a coffee shop, but visitors should be aware of their nature so you're not shocked to see someone light up a joint at the next table.
