Actually, the different DDR generations have different
shapes (they really don't want you to mess up and use the wrong one).
But it is pretty obvious which of the four generations you have, if you look at the current stick(s).
...
RAM also has a clock frequency, which is slightly harder to verify.
It is also fully compatible, i.e. PC3-10600 is slower than PC3-12800 but even if your motherboard only supports PC3-10600 a PC3-12800 stick will work, but simply run at PC3-10600 speeds.
You don't need Crucial's program to tell you what shape your RAM is, but it might be helpful to see what maximum speed you want.
There are programs (CPU-Z, Speccy) to identify your hardware on Windows, but on linux you can probably just examine the output of dmidecode.