A parameter query is one where, the user supplies criteria with which to filter the results.
When you run a normal query, it will return its results as soon as you run it.
When you run a parameter query, it asks you to enter a value. Once you provide the value, it will continue running, using the value as part of the filtering criteria.
The parameter is provided by the user at runtime. So a parameter query can return different results based on the user's input.
Dates are common parameters in parameter queries. This allows the user to provide a date with which to search. Numbers are also common parameters.
Parameter Query vs a Normal Query
There's almost no difference between creating parameter queries and normal queries. The only difference is that you use square brackets  to display text to the user.
Will result in this prompt when the user runs the query:
In this example, the date provided will be used to filter the results in the query to only those albums released after the date provided (because the query has a greater than sign > before the prompt).
Here's a step-by-step guide to creating a parameter query.