Answer:
A={x: x is a cat}
B={x: x likes climbing on trees}
My little cat Louis likes climbing on trees (Louis is in the intersection of the two sets)
A={x: x is a town in the USA}
B={x: x is a town in the UK}
To improve my English I'd like to go on holiday to a town in the USA, but a town in the UK would work too (the town shall be in the union of the two sets)