does firefox offer a firefox browser

Yes, it offers a browser: firefox.com/more/what-is-a-browser

No, it is not a search engine: blog.mozilla.org/en/uncategorized/internet-search-engine-browser

You can pick any of the built–in ones, or plug in any custom service you prefer: Manage Firefox search settings

Want firefox as a search engine and it never comes up as option to chose from as default browserI have downloaded firefox Beta

Firefox is a Browser to view internet sites. A search engine is used if you do not know the particular site you want to view.

If you know the site i.e. mozilla.org you can type that in the address bar.

Nowadays the address bar usually has a dual purpose and acts as the text box to search the internet, which search engine you use is up to you.

Bonjour

https://support.mozilla.org/en-US/questions/1603732