We've already kinda covered string, so I'll make it breif; Strings are a 'string' of characters, these are useful for storing words and generic data.
a := "This is a string!";
If you only wanted to store a single character instead of a word or several, you should use chars instead.
a := 'E';
Numbers are pretty self explanitory, they're a sequence of digits that make up a mutable integer you can perform mathemathical operations on.
a := 12345;
Arrays are a collection of values, to define you have an 'array' of values contained in square brackets seperated by commas.
a := ["first value", 2, 3 , 4, "last value", 6];
Then to access a value from an array you use a reference to the array (in mosts cases a variable, but you could also do
[1, 2, 3][2]
) followed by square brackets containing a number, just remember that arrays start from 0!b := a[2] # if a is [1, 2, 3] then b is now equal to 3