Hi guys.
It’s just a fast question because i couldn’t find my way on google so i’m asking people.
For example: when you add->mesh->landscape there will be a new box with properties in the Tool Shelf. Accidentaly i pressed tab and the box disappeared. I tried to tab again but nevermind, doesn’t work, don’t know how to bring it back.
Can you help me pls? 
don’t know how to bring it back.
You can’t. The options will available when you add the object until to carry out some other action.