The main difference is the sentence construction, rather than the meaning. Both are used for contrast. "Although" is used with the "cause" and "however" with the "effect" as Dufffy showed. Here are some examples for you:
Although you are far away, I can still help you. or I can still help you, although you are far away. (Different order, same meaning)
You are far away. However, I can still help you.
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Although I wanted tea, I will drink the coffee you brought me. or I will drink the coffee you brought me, although I wanted tea.
I wanted tea. However, I will drink the coffee you brought me.
We sometimes use "however" at the end of the sentence, but it is not as common:
I will drink the coffe you brought me, however.
I hope this helps.
Bruce