could can be used to show possibility or to be polite when you’re asking for something.
It could be that he was in love with her sister.
could you please shut up? (okay ni tak polite sangat)
could you please keep it down?
Also, you can use could to say refer something boleh dibuat or dibenarkan pada waktu lampau. Kira macam past tense untuk can.
In the past you could race horses in the tracks in the middle of Kuala Lumpur.
Of course, last but not least you can use could to say something conditional or imaginative.
If only I could fly.
If only I could be as cute as EJ.