Input parameter

I am new to SAP HANA and I have been browsing the below blog regarding input parameter.

SAP HANA Variables and Parameters

Below are the steps found in the blog to create an input parameter IP_PSTNG_DATE used to filter the column "posting date" with values "<=posting date". The column "posting date" should display the values less than the value provided by the user.

1. Create an input parameter, say IP_PSTNG_DATE

2.In projection, go to filter and create an expression like PostingDate<='$$IP_PSTNG_DATE$$'

I have below queries.

1. In step 1, while creating input parameter, what is the parameter type I need to select.

2. Can someone please elaborate on this step. How can we add expression in the filter on projection node.(I am assuming the step is referring to the

projection node in calculation view)