There are two main kinds of conjunction.
Coordinating conjunctions join items that are of equal importance in a sentence:
You can have ice cream or strawberries.
He plays football and soccer.
The weather was cold but clear.
I waited at home until she arrived.
He went to bed because he was tired.
Starting a sentence with a conjunction
You might have been taught that it’s not good English to start a sentence with a conjunction such as and or but. It’s not grammatically incorrect to do so, however, and many respected writers use conjunctions at the start of a sentence to create a dramatic or forceful effect. For example:
What are the government’s chances of winning in court? And what are the consequences?
Beginning a sentence with a conjunction can also be a useful way of conveying surprise:
And are you really going?
But didn’t she tell you?
It’s best not to overdo it, but there is no reason for completely avoiding the use of conjunctions at the start of sentences.