Conjunctions are joining words that are used for joining two ideas in the same sentence.
Here are some common conjunctions:
and but when after so because even if or while before until since although as long as
Using different conjunctions can change the meaning of your sentence, or change what you are trying to write.
Look at these two ideas:
Johnny went to the playground __________ Toby went to the playground.
Now look what happens when we use different conjunctions:
Johnny went to the playground and Toby went to the playground.
Johnny went to the playground after Toby went to the playground.
Johnny went to the playground but Toby went to the park.
Johnny went to the playground when Toby went to the park.
Make sure that you use the correct conjunction for your sentence.