Words like something, nothing or anything are very similar and can create confusion when using them. Here you can check the rules:
We use something in positive sentences: I want to eat something.
We use nothing when the verb is positive but the meaning is negative: There is nothing in the fridge.
We use anything in questions and sentences with a negative verb: Is there anything in the fridge? I haven’t eaten anything since the morning.
The same rules apply when using someone / somebody, no one / nobody, anybody if we talk about people or somewhere, nowhere, anywhere if we talk about places.
Here you can find an exercise to practise this. Good luck!