Transitions are just simple words (or sometimes can be phrases) that link two related ideas. They are used in a series of simple sentences or in compound sentences with conjunctions or semicolon.
Transitions are normally followed by commas. Transitions may begin the sentence. They are particularly common in formal situation and in writing. In spoken English they are often omitted.
The meal was delicious. Nevertheless, I felt that it was quite expensive.
To form a compound sentence, usually a transition is used with a semicolon. Some transitions may be use at various points within a sentence. In this cases, commas are used before or/and after the transition.
The meal was delicious; however, I didn’t like the dessert.
The meal was expensive; as a result, I have decided not to go there again.
However, I enjoyed myself very much.
My wife, however, enjoyed herself very much.
My wife enjoyed herself very much, however.