A multidimensional array is an array that contains one or more arrays. Many languages allow for multidimensional arrays that have two, three, four, five, or more levels. However, arrays that have more than three levels are often very hard for most people to manage.
The dimension of an array indicates how many indices you need to select an element. To access an element in a two-dimensional array you need two indices. To access an element in a three-dimensional array you need three indices.
You can imagine a multidimensional array as having rows and columns in a table. A two-dimensional array could have three rows and two columns, meaning that inside an array there are three arrays with two elements in each array.