You can use"带"all the time.It means both bring,take. But you can't use“拿”so often.It often means just take. So ,if you don't know which one use best,choose带。 As you learn more about Chinese,you'll know the differents. But Chinese will understand no matter which vocabulary you use:)

the two words are the same use as "bring" and "take"

"带"可以用在某些抽象abstract的东西上（文学性的） 比如：带走我的心 take my heart away ,take my soul away 但你不能说“拿走我的心” 对于一般的物体，带和拿是一样的。 比如：他带（走/来）了我的一本书=他拿（走/来）了我的一本书 对于人物，只能用“带” 上次吃饭，他把孩子带来了。但你不能用“拿来了”

“带”is similar to “carry”or “bring”,take somethings with you.“拿”always means take somethings by band,it emphasize by hand. Their emphasis different in different situation.

You mean whether they are interchangeable? Well, that depends on the exact situations. See if you can understand the following sentences: 1) 我拿着一支笔 我带着一张报纸 2）我把它拿走了 我把它带走了 The difference is obvious. When you use "拿"，it indicates you are taking it by hand, but “带”doesn't show any clue of the way to take it. For instance, "拿"means “totake”，while "带"means “to take with” But in some cases, they ARE interchangeable: 1)帮我拿一个苹果 帮我带一个苹果 They mean the same, and the last one is commonly used in spoken Mandarin. Unlike English, they can mean both "to take"and "to bring", depending on the exact direction of the action. 拿来and带来 means “to bring”，but“拿走和带走”means “to take” In addition, 拿 always refers to real things, whereas 带 refers to both real and abstract things. Hope this is helpful to you.