PDF is the most common file type you will find on TeachersToTeachers.Net. You can download and view these documents using Adobe Acrobat or similar PDF reader applications. You can also easily print PDF files but usually you will not be able to edit them.
A ZIP file is a number of files compressed into one and zipped up. The total file size is smaller than the combination of files would otherwise be and it’s therefore quicker to download. You can unzip a ZIP file by simply clicking or double-clicking on it.