It's an informal way to express a general sense of inclusiveness, often without being specific or definitive.
Here are some examples of how it might be used:
* "I'm pretty much anything for dinner tonight." (Means the speaker is open to a wide variety of options.)
* "Pretty much anything goes in this class." (Means there are few rules or limitations.)
* "Pretty much anything can be found online these days." (Means online resources are vast and diverse.)
It's important to note that the phrase is often used in a somewhat imprecise way, and the speaker might not actually mean "everything" but simply a very large proportion.