Transition words are the words which link sentences or paragraphs fluently with no abrupt change in ideas. In other words, transition words or phrases form two sentences into a sentence. There are many transition words which add information, conclusion, cause, information, comparison and so forth.
In the above sentence transition word used is, however. 'However' shows contrasts or differences in the opinion or ideas. As the person loves chocolate but in contrary will be trying the coffee flavor.