It is here! You can turn German verbs into nouns by capitalising the infinitive (the form with -en on it). Such nouns are always neuter.
Duolingo, being Duolingo, has already introduced these without explaining them, for example -das Essen-!
A closer translation for this sentence that I think we (native Eng. speakers) would actually say, which preserves the spirit of the original, is "He is always at his studies". But I didn't dare try it, because I was sure I would lose a heart!
The beim here is short for "bei dem", and it's there because "he is always studies" or "er ist immer Lernen" wouldn't make sense. You need a preposition (at, bei respectively) to connect it all together.