In Ruby, prepend and append are methods used to add elements to the beginning and end of arrays, respectively.

1. prepend:
   • The prepend method is used to add one or more elements to the beginning of an array.
   • Syntax:

     array.prepend(element)
     

     or

     array.prepend(element1, element2, ...)
     

   • Example:

     numbers = [3, 4, 5]
     numbers.prepend(2)  # => [2, 3, 4, 5]
     

     or

     numbers = [4, 5]
     numbers.prepend(2, 3)  # => [2, 3, 4, 5]
     

2. append:
   • The append method is an alias for the << operator and is used to add one or more elements to the end of an array.
   • Syntax:

     array.append(element)
     

     or

     array << element
     

     or

     array.concat(other_array)
     

   • Example:

     numbers = [1, 2, 3]
     numbers.append(4)  # => [1, 2, 3, 4]
     

     or

     numbers = [1, 2, 3]
     numbers << 4  # => [1, 2, 3, 4]
     

     or

     numbers = [1, 2, 3]
     numbers.concat([4, 5])  # => [1, 2, 3, 4, 5]
     

In summary, prepend adds elements to the beginning of an array, while append (or << or concat) adds elements to the end of an array. These methods are commonly used for array manipulation in Ruby.