Who should be corresponding author?

corresponding author should be one who has done most of the work and is able to carry out corrections advised by the reviewers. Corresponding author is the person who has complete knowledge about the study and provides the intellectual supervision as well as liable to reply the queries of readers.

Is corresponding author the main author?

This is a common doubt, especially at the beginning of a researcher's career, but easy to explain: fundamentally, a corresponding author takes the lead in the manuscript submission for publication process, whereas the first author is actually the one who did the research and wrote the manuscript.