Beginning Japanese Phrases Podcast #193: ~がいる/~がいます there is ~; ~ exist (used only for living organisms including human)
Beginning Japanese Phrases Podcast #191: ∼ なんです [used when explaining something or giving new information]
Beginning Japanese Phrases Podcast #190: ∼んです; ∼んだ [used when explaining something or giving new information; a casual form of のです/のだ; の (explanatory particle) relaxed intoん]