Chrome is owned by Google, as is Gmail. You do not have to connect your Gmail (if you have one) to Chrome to download/install, but if you do, it allows you to 'link' devices together. This means that if you access different computers with Chrome, you can simply 'log in' to your Gmail and have your Webpage Favorites/ Bookmarks copied across. It will also copy to your smartphone. This makes accessing your personal things very easy. It is still secure though; you're logging onto your own private account.
There should be a 'skip' option or something similar if you don't want to sign in.
IE was actually phased out (well, it's technically still available if you know where to look) with Windows 10 because it is a security risk and less stable than its competitor's web browsers. MS released a new browser to take its place, but Chrome is still better.