A placeholder is a container that is used to display content, such as text, table, picture, movies, sound, clip art, chart, SmartArt etc. A placeholder can be resized, moved and edited. In a PowerPoint placeholders are displayed in the form of a dotted rectangular box and are found in all the built-in slide layouts
Impress is the presentation (slide show) program included in LibreOffice. You can create slides that contain many different elements, including text, bulleted and numbered lists, tables, charts, and a wide range of graphic objects such as clipart, drawings, and photographs.
A slide transition is the visual effect that occurs when you move from one slide to the next during a presentation. You can control the speed, add sound, and customize the look of transition effects.