So you're able to choose your own language for your character! That's great, because there's a lot of variety and flavour in D&D languages, which can help you shape a unique and interesting character.
You can choose a new language from the following list. On the right you can see what creatures usually speak this language.
Alternatively, you can use the following list. This list contains exotic languages: languages that are less common on the Material Plane and are often spoken by creatures from different realms or are quite rare.
With your GM's permission, instead of choosing a language from the list above, you can choose an Exotic language from the list below. On the right you can see listed creatures that usually speak this language.
These languages are languages that are very rare, and often not more than one or two species in the Multiverse speak these languages. Unless the GM allows you to, these languages cannot be spoken or understood by a player if they don't have a special ability for it.
An example where one would be able to understand such rare languages, is a Ranger who chose a Favored Enemy that speaks one of these languages and hence learns it.
On the right, you can find what creatures usually speak this language.