IELTS Grammar: while, whilst, whereas, as

 Joshua asked me the following question:

"Can you explain while, whilst, whereas, as? Either can be used to connect two sentences, but I am not sure how to identify them and quite often I use them wrongly."

Here's my simplified explanation:

1. While and whilst are the same, but whilst is a bit more formal (according to one famous grammar book).
2. Whereas is always used for contrast. While/whilst can be used for contrast, OR to mean "at the same time".
3. As can mean "because" or "exactly at the moment when".

Try to write an example sentence using each of these words. Feel free to share your sentences in the "comments" area below.