Pictures on computers come in two flavours: bitmaps and vector pictures. For a quick idea of which is which, let's say that bitmaps are usually edited with softwares like photoshop (or gimp if you use free software), and vector pictures are edited using softwares like Adobe Illustrator (or Inkscape).
Most softwares can display and read bitmaps, so they tend to be easier to share. Their main problem is that you can't zoom well on them. Bitmaps are basically mosaics made of small square dots, called pixels; if you zoom, those small square dots will become large squares. A bitmap fit for screen display will probably print poorly; a bitmap fit for printing will need to be in a very high resolution. However, sharing vector pictures is sometimes difficult (for no good reason, but it's a sorry state of affairs), so you might end up sending high-resolution bitmaps for printing. note from 2025: things are much better now.
To export a bitmap, choose the "File/Export As/Export as Bitmap" menu entry.
You can export a jpeg or png version of your text. If no text is selected, the whole text will be rendered. If there is a selection, only the selected text will be drawn.