I am pretty lost with the attribute table, so I couldn’t figure out the already existing answers about it (using QGIS 2.12.3.). I have a shapefile with all the protected areas in one region. Since I don’t need all of those protected areas, I would like to know how I can hide all the other objects? I have to search for the objects through their name and really don’t know how to use the dialog with all its functions.
What you're looking for is called a definition query. There is a tool for it in qgis called query builder.
Select the field your names are stored in and type the name of the protected area to display, i.e:
"NAME" = 'Example Area'.
You may want to look at this post, it explaines the use of the query builder in further details: Displaying only selected features on map in QGIS? or also: http://docs.qgis.org/2.0/en/docs/user_manual/working_with_vector/query_builder.html
I hope this explains what you want to achieve.