These types of designs go by a number of names, rather than just one.
The specific example in the question is a sample of redwork, so named for the thread color; it's also often stitched in blue and called bluework as a result. These designs are typically quite simple, using only very basic stitches; Spruce Crafts offers more information and examples of redwork embroidery, as well as tips for executing this style of embroidery.
Change your thread to black, and now you have blackwork, which frequently incorporates geometric and "counted" designs, fill patterns, and even additional colors. Traditionally, it was largely focused on patterns, but modern blackwork will often be more figural, as your example shows. Spruce Crafts again offers more information, as well as historical patterns.
Switch to metallic thread, and you have goldwork, which tends to have more line weight variation and solid (textured) fills than the previous styles, while still also exhibiting designs that are more focused on just the outline. Royal School of Needlework's page has examples of both filled (textured) and open (linework) designs, as well as hybrids of the two.
If you work in a light color on a dark fabric, using a running stitch, you're likely looking at sashiko stitching; while, like blackwork, it typically involves repeating semi-geometric patterns and emphasizes traditionally Japanese design elements, modern designs incorporate more figural work. Spruce Crafts has examples of both traditional designs and those adding figural elements.
And if all this monochromatic stuff isn't your style, vintage embroidery changes up the line colors throughout the designs, instead of utilizing fills or textures. Spruce Crafts again has some examples and patterns for these styles.
Lastly, if you're looking beyond hand embroidery, machine embroidery companies tend to class designs like these as light stitching, as seen with the category search on Urban Threads (many of whose designs are also available for hand-stitching). While not exclusively outlined designs, many "light stitching" machine patterns have a similar look to your example.
Note: I have no affiliation with the site Spruce Crafts; they are simply the site that came up most often with good examples in a basic Google search.