.ppt files are created and opened using Microsoft's PowerPoint application. PowerPoint is a presentation program and is mostly used for displaying digital slides during business/educational presentations and is also widely used for displaying picture slideshows received by email.

PowerPoint belongs to the Microsoft Office suite and is available for both the Windows and MAC OS operating systems. PowerPoint is now arguably the standard way of displaying slides, making the slide projector virtually redundant.

The .ppt file can contain a combination of text, pictures and even movies. These files are all held within the actual .ppt file, so you only have one file to distribute or receive. The .ppt file also holds information on how the presentation is displayed, such as the transition effects between slides.

PowerPoint also saves presentations in .pps (presentation), .pot (template) or .pptx (PowerPoint 2007).

There is no real difference between a .PPT and a .PPS file. You can even rename the extension and they'll still work. The difference lies in how PowerPoint treats the files, a .PPT file will instruct PowerPoint to open the file in 'edit mode' whereas a .PPS file indicates that the slideshow should be opened in 'Play mode'.

To create/open a .ppt file, you will need PowerPoint (part of Microsoft Office suite) or PowerPoint Viewer 2007, which is available free from Microsoft's website (link below).