Please Help me Understand dynamic MQuery Paramters

Dynamic parameters let you bind a parameter to a column. Any time that column is used to filter a visual that uses direct query, the parameter will be substituted for that filter value and the M query will be revaluated. Filtering can be from slicers or from visual when a user select part of the visual. Note: SQL is not supported. Now my doubts are - 

1. does dynamic parameters only apply to tables using Direct Query?

2. What is the advantage of dynamic parameters over slicers, I feel like achieving the same using slicers, so what exactly is the advantage?

Please help, thank you.