What is the difference betwen boost::multi_array views and subarrays

After looking the documentation I cannot figure this one out.

I can write code such as

typedef boost::multi_array<boost::int32_t, 3> data_t;

// 3d --
typedef data_t::array_view<3>::type data_3d_view_t;

// 2d --
typedef data_3d_view_t::reference data_2d_subarray_t;
typedef data_t::array_view<2>::type data_2d_view_t;

Then I can access a 2d slice using via the types data_2d_subarray_t or data_2d_view_t.

What is the difference between them ?
What can I do with one that I cannot do with the other ?
Is it there any performance difference ?

Thanks a lot for clarifying this to me. Best regards, rodrigob.