Intel separates the gap between i3 and i5 processors that makes it easier for us to identify between the dual core and the quad core. The main difference between them is that all i3 processors came in a dual core and i5 has quad core.
Another big difference between them is that i3 has the hyper threading and the i5 don't. In contrary, the i5 processors do have a turbo boost and the i3 don't have it.
What the Turbo Boost Does?
The turbo boost in i5 and i7 processors has the ability to gain more speed in your processors frequency when activated. You can add an extra 300MHz to 400MHz for i5 and i7 that can push you further. To give you an example on this, an intel i5 2300 2.8 GHz can be boost up to 3.1 GHz and an i7 2600 3.4 GHz can be boosted up to 3.8 GHz. This is the main advantage of the i5 over the i3.
What is Hyper Threading?
Hyper Threading is an intel technology that is capable of logic core duplication. This allows each physical core to be used as two logic cores. The result for this is that Windows OS will identify them as two giving your dual core i3 a quad core. The i5 don't have this features and this is the big plus factor of the i3 processors over the i7.
As you can see the big difference between them, the i5 has a huge advantage over the i3 in terms of speed performance.
Intel finally came up with a lower cost processor for a budget conscious mind user. For an average computer user the intel core i3 is a perfect choice and for a more advanced who wants an extra push the core i5 is more appropriate for them.