Identifying NVR and Camera types

I want to make sure that I keep my firmware up-to-date on my Hikvision setup. However I do get a little confused by the terminology used.

Hopefully my question won't seem too stupid!

For instance I see that there has been a firmware update issued just this week for 'I series' units. What I don't know is, which is the letter that is used from the product identification number to show which 'series' it belongs to?

My setup consists of just one NVR and one camera (at the moment) My NVR is...

Identifying NVR and Camera types