ODP is one of many formats that were born from the Open Office Project. The project was initiated by Sun Microsystems as an answer to the ever rising demand for free office applications. There are many applications that have bought into this, including KOffice and Neooofice. ODP is used by Open Document Presentation files that are created by the OpenOffice software suite. Open Document Format is XML based and therefore easily portable.
ODP files can be opened and edited on applications whose standards are in conformity to the OpenDocument format. The Impress presentation application that comes with StarOffice from Sun Microsystems (now Oracle) can also render ODP files in a similar fashion to OpenOffice. As it's open source, any user can modify the source code to enhance the application and later on publish their modified copies for public consumption.
PDF is a file format developed by Adobe Systems for representing documents in a manner that is separate from the original operating system, application or hardware from where it was originally created. A PDF file can be any length, contain any number of fonts and images and is designed to enable the creation and transfer of printer-ready output.
Each PDF file encapsulates a complete description of a 2D document (and, with the advent of Acrobat 3D, embedded 3D documents) that includes the text, fonts, images and 2D vector graphics that compose the document. They do not encode information that is specific to the application software, hardware, or operating system used to create or view the document.