Something that is "obvious" is really easy for anyone to see and understand. Here are some examples:

Someone asks you a very simple math question, so you say:

Oh, that's obvious. The answer is 42.

Your friend seems angry every time he talks about his brother. You ask about it, and he responds:

You: You and your brother don't get along, do you?

Him: Yeah, not really. Is it that obvious?

One way to use "obvious" is with "it is" or "it was" like in these examples:

It was obvious to me that I wasn't welcome there.

It's obvious that we're not going to be able to fix everything, but let's at least try to make things a little better.