What can my company see if they install iCloud on my company iPhone?

My company has an AT&T business account and I have an iPhone 5 through this plan. Our IT guy has insisted installing a company iCloud account on our phones and I was wondering what he/my company would actually have access to see… Messages? Emails? Photos?

If so, is there any way to limit what they can see? And can I have two iCloud accounts on one phone?

Please don't send me a link to another site. I've tried to google this but I just want a simple and accurate answer… Thanks so much in advance!

Added (1). This isn't MY iCloud account. My IT guy won't let me use my personal iCloud account. It's a company-made iCloud account, so I won't have the password. My IT guy will have the password.

You already have icloud, you do not need to install anything. You will be the only one that knows the password also as you use your normal apple id password.