We can infer from Aristotles descriptions that aesop was a freed slave, but little else is known about him?

what type of sentence

This is a compound-complex sentence.

It means that it contains at least two independent clauses, and at least one dependent clause. As you can see here, there are two independent clauses:

1. We can infer from Aristotle's descriptions

2. but little else is known about him

And there is one dependent clause - that Aesop was a freed slave.