Learn Dutch: Hij interesseert zich voor de fotografie.

There is no difference in meaning! There are two common ways to say you are interested in something in Dutch. You can use the adjective geïnteresseerd with the fixed preposition in (Hij is geïnteresseerd in...). Alternatively, as shown in this sentence, you can use the reflexive verb zich interesseren, which always pairs with the fixed preposition voor (literally "to interest oneself for").

Why do we need the word zich here?

Zich is a reflexive pronoun (like "himself" or "herself"). Because this sentence uses the verb zich interesseren, it requires a reflexive pronoun that matches the subject. For hij, zij, or u, that word is zich. If the sentence were about you, it would be: Ik interesseer me voor de fotografie.

Why does the Dutch sentence say de fotografie instead of just fotografie?

In Dutch, abstract concepts, academic subjects, and arts often take a definite article (de or het) to refer to the field as a whole, whereas English usually drops the article. It is also grammatically correct to drop the article and just say fotografie here, but adding de is very common and natural in Dutch.