Depth of field signifies to the area of your photograph that is in focus. Depth of field can range from very tiny subjects in focus to a very wide background in focus.
For quick and observable impact on the depth of field of your photograph you can change the aperture of your lens. The smaller the aperture (a large number) the greater the depth of field, the wider your aperture, the narrower your depth of field.
So, shooting with wide aperture values, in the range of f/1.8 to f/3.5 will result in an image with a narrow section of your subject in focus and much of the background out of focus.
For further explanation and more tips check the Infographic below.