Expresses contrast or contradiction between two clauses; 'A, but B', 'A, however B'.
Sentence A + しかし + Sentence B.
Long explanation:
The grammar point A。しかし、~B。 is used to show contrast or contradiction between two clauses. It can be translated as 'A, but B' or 'A, however B' in English. しかし is placed between two sentences to indicate a contrast between them.