What are iPhone models and generations? Is my "iPhone 11 Pro" the latest model in 2019?

Yes, your "iPhone 11 Pro" is the latest model in 2019.

Technically, "iPhone 11 Pro" refers to a model family. Usually, there are several models in a model family sold in different regions. For example, "iPhone 11 Pro" has 3 models:

A2160 (Canada, United States),
A2217 (China mainland, Hong Kong, Macao),
A2215 (other countries and regions)

Since 2007, Apple has produced many iPhone generations and model families as listed below:

Generation   Model Family        Supported Period
----------   -----               ----------------
iPhone 11    iPhone 11 Pro Max   2019–present
             iPhone 11 Pro       2019–present
             iPhone 11           2019–present
iPhone X     iPhone XS Max       2018–present
             iPhone XS           2018–present
             iPhone XR           2018–present
             iPhone X            2017–present
iPhone 8     iPhone 8 Plus       2017-present
             iPhone 8            2017-present
iPhone 7     iPhone SE           2016–present
             iPhone 7 Plus       2016–present
             iPhone 7            2016–present
iPhone 6     iPhone 6S Plus      2015–present
             iPhone 6S           2015–present
             iPhone 6 Plus       2014–2016
             iPhone 6            2014–2016
iPhone 5     iPhone 5S           2013–2016
             iPhone 5C           2013–2015
             iPhone 5            2012–2013
iPhone 4     iPhone 4S           2011–2014
             iPhone 4            2010–2013
iPhone 3     iPhone 3GS          2009–2012
             iPhone 3G           2008–2010
iPhone       iPhone              2007–2008

⇒ iPhone Model: 5C, A1532, or ME505LL/A

⇐ Understanding Your iPhone

⇑ Understanding Your iPhone

⇑⇑ Apple iPhone - Frequently Asked Questions