A few years ago you could simply order a smartphone online or go and buy it. You can still do this, but you must be careful. The reason why you must be careful is Chinese copies! Their first copies were very different from original phones, so anyone was able to tell the difference, but today, it is almost impossible to notice the difference. Because the two most popular smartphones at this time are iPhone 6 and Samsung Galaxy S6, there are many copies of them. When you are buying a phone in the shop there is no risk, but when you are ordering it online, the risk is high.
On photos, you simply cannot tell the difference between the original phone and cheap copy. In a case of iPhone, a situation is a bit easier. The Chinese copy runs on Android 4.4.2, which looks like the iOS. The things that look a bit different are a keyboard (you must know how the original iOS keyboard looks like) and a Google Play icon. As you may know, iOS don’t support Google Play. If you see some of this, this is a copy. Also, the home button isn’t so well made as on the real iPhone.
The situation is even more complicated with the Galaxy S6. They both run on Android and look the exactly the same. The only difference you can notice are the main camera (the look of it is different on the original) and the charging port is opposite on the Chinese copy. Look on the internet how the real charging port looks like and compare it with the phone you are buying.