It is expressing a small number of options, usually between two options. She likes to play either netball or badminton; this suggests that she likes both netball and badminton but nothing else. I think that he will either go out for dinner or see a movie tonight; This suggests that he will choose 1 of the two options but not both. Either mum or dad will pick me up; As the previous example, it suggests that only mum OR only dad will pick the person up. You can either eat chocolate or ice-cream; similarly to the first example, it suggests that you only have the option of eating chocolate or ice-cream. You can eat either chocolate or ice-cream; this has the same meaning as the previous one but sounds a bit softer. I hope this helped (-: