Graphics in your designs are primarily based on vector objects (paths and shapes). These objects appear on the canvas as anchor points and curves. Internally, they are mathematically defined via coordinates of anchor points and curvature of lines that pass through those points. Due to this, vector graphics can be scaled with no quality loss.
All drawing tools in the program create objects that are based on paths. A path is a thin vector line that enables you to edit it. Paths are explained in detail in the Path and its Features section.
You can apply a number of properties such as stroke or fill to a path to make the object look as you need. Although the path itself is vector, some effects that you can apply to it can be raster-based (e.g., gradient fill or shadow). In case of such combination of vector and raster graphics, you should take into account the resolution of the raster parts.
Text is also vector. It is based on glyphs provided by a selected font. You can convert text to paths in order to edit the shape of individual characters.