ODP is the native text file format from the OpenOffice office suite (or Apache OpenOffice). The format was developed by Sun Microsystems. Its name is an abbreviation for OpenDocument Presentation. The ODP extension is commonly used to create presentations. To create ODP files, the open XML standard OASIS OpenDocument is used. Since 2010, the popular Microsoft PowerPoint program can also work with ODP files. A presentation in ODP format can exist in the form of a set of slides, which include text (including formatted), graphics, various effects.
PPTX is a more modern and convenient presentation format in the popular Power Point application, which replaced PPT after entering the Microsoft PowerPoint 2007 market in updated office suites. Full name - Microsoft PowerPoint Open XML Document. Designed for the same purposes as PPT - creating a presentation in an editable slide show format. The difference from the first version is that the PPTX file is created using the open XML format. If in the PPT format the data is stored in one binary file, then in the PPTX format - in a compressed ZIP archive as a collection of separate files.