What is the difference between deutsch language and German language?

There is no difference between "Deutsch" and "German". They both refer to the same language: the language spoken in Germany, Austria, Switzerland, and other parts of Europe.

* Deutsch is the German word for "German". It's the language's endonym, the name used by native speakers.

* German is the English word for the language. It's the exonym, the name used by speakers of other languages.

So, you can use either "Deutsch" or "German" to refer to the language. They both mean the same thing.

It's similar to how the French language is called "Français" by native speakers and "French" by English speakers.