A compound sentence is made up of two main clauses connected by a coordinating conjunction. They are used to connect sentences. We can use the acronym FANBOYS to help us remember the coordinating conjunctions (For, And, Nor, But, Or, Yet, So)

For

For is used most often as a preposition, but occasionally it may be used as a coordinating conjunction to indicate a reason. Its use is often considered archaic.

• John thought he had a good chance to get the job, for his father was on the company's board of trustees. (for + main clause)
• Most of the visitors were happy just sitting around in the shade, for it had been a long, dusty journey on the train.

And

And is commonly used as a coordinating conjunction, but it is often overused. And does not provide a particularly sophisticated indication of how two ideas are connected, so it is often better to find some other way of connecting two ideas.

• A pilot scheme, although successful in many respects was deeply problematic and was eventually abandoned in 1993.
• This lead to Parnell's release from prison and the anger that surrounded the land issue in Ireland abated for a while.

Nor

Nor may sometimes be used as a coordinating conjunction. It is often used with the conjunction neither (Neither ... nor). Notice the word order:

• The microbial aerosols did not persist for long periods, nor was there evidence of spread to adjoining areas.
• A European leader would neither have resorted to such a metaphor, nor subscribed to the thesis of a clash of civilizations.
• The committee did not attempt to make aesthetic judgements, nor did the artists assume expertise in the issues.

But

But is commonly used to indicate a contrast between two clauses.

• Sherds of Roman pottery were recovered from most contexts but all the sherds were much abraded and likely to be residual.
• The operator steers up until the point where the robot takes over, but retains control of the brake and accelerator pedals.

Or

Or  is used to introduce two options.

• Chemotherapy may be used for palliation when other techniques have failed or when significant disease is present.

Yet

The word yet is most commnly used as an adverb, but in some cases (and often in academic writing) it may be used as a coordinating conjunction to indicate a contrast (similar to but):

• That would not be translation, yet that is what is happening when we translate Adam as man early in Genesis.
• He showed no signs of mental or physical trauma, yet appeared to have suffered total amnesia.

So

So may be used as a coordinating conjunction to indicate the reason for something or to summarise the writer's position. Compare:

• Jason Donovan won libel damages over inaccurate claims about his sexuality, so it is still considered actionable.
• So..... to stop back pain recurring, keep fit and stay active.