What is different between 分かります and 分かりました。
A very good question.
Despite how it might look on the surface, this is definitely not a question about tense.
We use the two phrases differently depending on the situations -- more specifically, on the content of the discourse. In other words, it depends on what the other person has just said to you.
You use 「わかりました」 when you understand the explanation or instruction that the other person has just given to you. It is an expression of comprehension of and obedience to what has been explained to you. You just learned something now.
Guy: "To get to the XXX Park, you go ~~~~~."
You: 「わかりました。ありがとうございます。」 You will never say 「わかります」 here.
「わかります」 is quite different in that it is used to say "Yes, I know." or "I know what you mean." It is an expression of knowledge and sometimes, sympathy.
Guy: 「『懐疑的』の意味はわかりますか。」"Do you know what 懐疑的 means?"
Woman: "My husband just sits in the couch and watches TV ~~~~~. He never helps me with ~~~~."
You:「わかります。My husband is the same way.」