How is a slice in Go structured and how does it differ from an array?

In Go, a slice is a structure that describes a sequence of elements of the same type but does not contain data itself; it only points to an array in memory.

A slice consists of three components:

• a pointer to the underlying array,
• length (the number of elements accessible through the slice),
• capacity (the maximum number of elements that can be stored starting from the pointer).

Differences between a slice and an array:

• An array is a fixed-size sequence of elements, with size defined at declaration and not changeable.
• A slice is a dynamic structure that can change its length (through append and other operations).
• An array is passed by value, whereas a slice is passed by reference to the array, making it more flexible and efficient to work with.

Example:

arr := [5]int{1, 2, 3, 4, 5}      // fixed-size array
slice := arr[1:4]                  // slice with elements {2, 3, 4}

slice = append(slice, 6)           // slice can expand, possibly allocating a new array

Thus, a slice is a convenient and flexible way to work with sequences in Go, hiding the details of memory management.