How'd they do that? - What does 'd mean?

[Tung Quoc]

Dear teacher,

1.On TV, I always see the program whose title is:

How’d they do that?

What does “’d” mean?

2. Please read:

A: He's cute. What his name?
B: Well,it's a "she" really. Her name Fluffy.
A: Can I hold her?
B: Of course.
A: Ouch!Why’d she do that?

What does “’d” mean?

Quoc

[Yankee]