Here is some information on different file types:
.txt This is a text file and can be opened in Notepad, Wordpad and Word. This is used for creating basic text and has no formatting options. This is also referred to as ASCII file and is a generic format that can be ready by a variety of text editors
.rtf This is a Rich Text file and can be opened in Wordpad and Word. This is used for creating text files with basic formatting options. A generic Format format that can be read by a variety of text editors
.doc This is a Word Document and can be opened in Word. This is used for creating Word documents with a variety of formatting options and other features
.dot This is a Word Template and can be opened in Word. This is used to create a Word template, on which other Word documents can based
.csv This is a Comma separated comma delimited file and can be opened in Excel. This is a generic format that can be read by a variety of spreadsheet and some database applications. Creates a list of records where each column value is separated by a comma
.xls This is an Excel Spreadsheet and can be opened in Excel. This is used to create an Excel Spreadsheet
.xlt This is an Excel Spreadsheet template and can be opened in Excel. This is used to create an Excel Template, on which other Excel spreadsheets can be based
.ppt This is a PowerPoint presentation and can be opened in PowerPoint. This is used to create a PowerPoint Presentation
.pot This is a PowerPoint presentation template and can be opened in PowerPoint. This is used to create a PowerPoint template, on which other PowerPoint Presentation presentations can be based
.pps This is a PowerPoint show and can be opened in PowerPoint. This is like a PowerPoint Presentation, but containing information for running a presentation. This file will open in Slide Show view
.bmp This is a Bitmap and can be opened in MS Paint or Picture Manager (among others). This is a graphic file format for use in presentations or documents. Can not be used on the web and can be very large in file size. Not suitable for photos
.gif This is a Gif and can be opened in MS Picture Manager or PaintShopPro (among others). This is a graphic file format for use in presentations or documents or on the web. Limited to 256 colours. Lossless (will not lose details repeatedly saved). Not suitable for photos. Small file size
.jpg or .jpeg This is a jpg file (Joint Photographic Experts Group). This can be opened in MS Picture Manager or PaintShopPro (among others). This is a graphic file format for use in presentations, documents or on the web. Best format to use for photos. Lossy (will lose details when repeatedly saved). Small file size
.png This is a PNG file (Portable Network Graphics). This can be opened in MS Picture Manager or PaintShopPro (among others). This is a graphic file format for use in presentations, documents or on the web. May not appear on older versions of web browsers. Lossless (will not lose details when repeatedly saved) but can be used for photos. Larger in file size than gif or jpg