HOWEVER and ALTHOUGH are Discourse Markers. This means they can show the connection between what a speaker is saying or what has already been said. they show a contast.
HOWEVER emphasize the fact that the second point said in an sentence contrasts with the first. e.g. : I don't like the job much. HOWEVER, the money is ok. The train was an hour late. HOWEVER, i managed to get to the meeting in time. However is separated by a comma (,) wfrom the rest of the sentence.
ALTHOUGH is also a linking word, expressing contrast. e.g. : ALTHOUGH i enjoy his company, i don't want him here all the time. ALTHOUGH she read the novel, she wasn't able to talk about it. Although is usually placed at the beginning of its clause .