There are a few important differences between the first and second iterations.
The second iteration comprises the unfilled positions that are left over from the first iteration. Overall, there will be fewer available positions in the second iteration than in the first.
Furthermore, the second iteration follows the same structure as the first iteration, but on a more compressed schedule.
Whereas in the first iteration, there are separate quota for IMGs and CMGs, in the second iteration, all listed positions are available to all eligible applicants. There may be exceptions to this rule. For example, Ontario and Alberta programs will keep both IMG and CMG streams separate in second iteration, as it is in first iteration. So please review the provincial criteria section and program description pages, posted on the CaRMS website for further information.