Algorithm
An algorithm is a method or process to solve a particular problem
Array
An array is a collection of items, encapsulated into a single, neat unit. Arrays are generally used to keep closely related items together; a list of colours, names, etc..
Assignment
You assign a value to a variable. Assignments are done using a single equals sign. For example - $myVar = 5 - here you are assigning the value of 5 to $myVar