What does 104 mean?

It means 10 multiplied 4 times

104 = 10 × 10 × 10 × 10

Similarly

5
^{
2
}
= 5 × 5

2
^{
3
}
= 2 × 2 × 2

4
^{
8
}
= 4 × 4 × 4 × 4 × 4 × 4 × 4 × 4

3
^{
5
}
= 3 × 3 × 3 × 3 × 3

Here,

10
^{
4
}
is called 10 to the power of 4

5
^{
2
}
is called 5 to the power of 2 or 5 squared

2
^{
3
}
is called 2 to the power of 3 or 2 cubed

4
^{
8
}
is called 4 to the power of 8

3
^{
5
}
is called 3 to the power of 5