SSIS 2012 in new Project Deployment Model contains Parameters both on Project and Package Level. One of the column for parameters is called Required. For more information visit SSIS 2012 Project Parameters
Required False means that the value (design value) we provided in SSDT will be used during deployment (unless we use a deployment method where we provide the value) and TRUE means that we have to explicitely provide the values (=required) so after deployment Parameter Value is blank.
To better understand it let me provide some examples with images
In the image below you can see I have a project with one Project Parameter and one Package Parameter with Required column set to FALSE
Using SSDT I deployed the project and we I click package configure with Scope 'Entry-Point packages and project' that shows my Package Parameter and Project Parameter. You can see that Value column is filled and and matches values I provided in SSDT. So that is what we will get if we use Required FALSE (unless we use deployment where we specify values or another method).
IMPORTANT: Required False is quite risky and may introduce accidental mistakes during deployment. Personally I intend on setting Required always to TRUE so there is no room for issues (unless I forget to set it).
In second example we have the same set up but this time we set Required column to TRUE for both Project Parameter and Package Parameter.
Using SSDT I deployed the project and checked the same dialog box Configure - SSIS 2012 Project Parameters.
You can see below that setting Required to TRUE means that the Value is NOT populated using values from SSDT (Design Values).
I hope this clarifies how the required column works for parameters in SSIS 2012.