A context object in MVEL is an optional enviromental element that can be used in conjunction with, or an alternative to, injected variables into the parser/interpreter. 

For example: 

In this example, we're using the test String object as our context object, allowing us to execute the toUpperCase() method as a local function in our expression.  We can also access other methods in the java.util.String class as bean properties.

Consider:

Now, just for example purposes, lets apply this class in one of our tests:

In this example, the value of the variable name returned by the expression will be "Bob".