What are the differences between sharing and emailing checklists?

Sharing a checklist copies the checklist and places it in another user's account. These observations then go toward the calculation of their species counts, checklist counts etc. in addition to yours.

Emailing a checklist does not copy the checklist but forwards it to folks including yourself who you think would be interested in your findings. It does not affect their calculation on eButterfly (i.e. life lists).