Does this move from IPhoto to Photos mean that all my photos are now public on ICloud and did I give permission for this to happen?

Does this move from IPhoto to Photos mean that all my pics are now for public display on ICloud and, if so, was permission given to do this?

No.

First of all, you do not need to migrate from iPhoto to Photos. iPhoto is supported on Yosemite. Just update to iPhoto 9.6.1 for compatibility with MacOS X 10.10.3 or later and continue to use iPhoto for the time being. Barney-15E's user tip explains how to update to iPhoto 9.6.1 by reinstalling. See this link: Get iPhoto 9.6.1 if you didn't update before OS X 10.10.3

If you are using the new Photos.app and migrated your iPhoto Library to Photos, your photos will only be in iCloud, if you enabled iCloud Photo Library in the Photos > Preferences > iCloud. After all, you will need to sign p for more iLoud storage and pay, if you want to keep a large photo library in iCloud.

And even if you enabled iCloud Photo Library your photos are not public. You need your Apple ID and and your password to access the iCloud Photo Library.

They are only on iCloud if you turned on iCloud Photo Library.

Even if you turned on iCloud Photo Library and your photos are there, they are not public. Your Apple ID and password (and possibly more if you have 2 factor authentication turned on) are needed to access them.

If you want to share photos, that is possible by using iCloud Photo Sharing but that requires additional setup steps: iCloud Photo Sharing FAQ - Apple Support