Wilcoxon Rank sum - urgent

Hi
i have a stats exam tomorrow, and looking through my notes, i do not understand Wilcoxon rank sum at all. To me it makes no sense, and looking online has confused me even further. Would anyone be able to explain it to me? Possibly with an example?

Thank you so much in advance
xx

i still dont understand it. I dont understand how i apply it to numbers. If i give you the question, would there be any chnace you could help? You would be an absolute star if you would.

A psychologist wanted to know whether the liking of a food was influenced by whether it was paired with images of obese or anorexic body shapes. The following preference ratings were given by people who had the food paired with either obese or anorexic images. Is there a significant difference?

Obese paired: 3, 5, 1, 4, 2, 2, 1, 10
Anorexic Paired: 5, 6, 7, 7, 8, 6, 9, 8, 6

H0: population median difference =0
H1: Population differnce does not = 0
two-tailed test

3-5 = -2
5-6= -1
1- 7= -6
4-7 = -3
2-8 = -6
2- 6= -2
1- 9 =-9
10 -8 = 2

T+ = 2 T-= 29 CV= (at 5% level) = 4

as 2 < 4 ( TS <CV) Reject H0 and conclude that there is a signicant evideence to show that preference ratings were given by people who had the food paired with either obese or anorexic images