In a response "any" is negative, "some" is positive. I didn't know anyone at the party, she doesn't want any more coffee, we didn't go anywhere special. I know someone who lives in Bogota, he wants some more coffee, he went someplace on vacation. In a question both are OK but I use "some" when I want to hear "yes" as the response; I have some nice bananas for sale... would you like to buy some? Good question!

"Someone" is more specific (especially in number). "Anyone" is more general. Anyone can use italki, and someone will be from Colombia. Anyone can learn English, and someone can teach them.

"Someone" implies that the speaker is looking for/talking about only one specific person. Example: I'm looking for someone who can paint my apartment for $100. Example: The police said someone robbed the bank yesterday. "Anyone" implies that the identity of the person doesn't really matter. The statement is more of a generalization. In Spanish, it's like "cualquiera persona." Example: Anyone who drives drunk is irresponsible. Example: I don't like anyone who is cruel to animals. Be aware that sometimes native speakers use the two interchangeably because sometimes the specificity doesn't matter. For example, it's fine to say: "Is there someone who knows the answer to this question?" or "Is there anyone who knows the answer to this question?" and "Can someone help him?" or "Can anyone help him?" They mean the same thing to me.

Anyone means talk to any person, for example: You have a problem and your willing to talk with any person. Someone ,a person you know are anybody . Here is an idea you have a problem with your credit then you would talk to someone that knows about credit.

They are close and many times are interchangeable. There are some differences, though. You would use 'anyone' in negative and question sentences. "I can't find anyone." "Can anyone help me? You would use 'someone' in affirmative sentences. "Don't worry. I have someone helping me." There dividing line is not always clear, but this should help.