"Adobe PDF is a universal file format that preserves all of the fonts, formatting, colors, and graphics of any source document, regardless of the application and platform used to create it. PDF files are compact and can be shared, viewed, navigated, and printed exactly as intended by anyone with a free Adobe Acrobat Reader." (From Adobe's website)
All the forms offered on the SBE's website use Adobe PDF.
CSV stands for "comma separated values." A file in CSV format is a plain text file where all values (text, numbers...) are separated by commas and, often, enclosed with double quotes. Because they are not application-specific, CSV files can be opened on any computer system and by most any application. You can easily import data from a CSV file into KSpread, FileMaker Pro, Excel etc..
A "ZIP file" is a file containing compressed data. Large files on the SBE's website are available as ZIP files to reduce as much as possible your download times. You will need specific utilities to open ("expand") ZIP files. These utilities are available free for most platforms.
The following list is provided for your convenience but does not represent the diversity of compression software available on the market.