Share Formats

I'm on OSX 10.10.2. iMovie version 10.0.6

iMovie has lots of share options. I'd like to learn what format they are putting the movies in without trial and error. Where can I read about what each option is doing? Automation is nice but I want to know what is going on.

Also, call me old school, but I like to use the file option and then upload manually when I am ready but want to use the autobots setting if I agree with the suggestion. I've lost some hours uploading to YouTube just to have it fail and then can't find the compiled file and have to start over. Maybe someone can tell me where iMovie is hiding the goods and how it names it after compile before upload. I also upload to my account, wife's and kid's accounts and find switching accounts and uploading is easier in Chrome.

Thanks.