How to shoot a blurry background using aperture
Creating a blurry background can be done a few different ways, but understanding and utilizing the aperture in your lens is a great starting point and will allow your subject to 'pop' off the background and illuminate distracting elements.
The blurred look (foreground or background) is achieved through the manipulation of depth of field, which is the distance of what is in focus between the camera and subject.
Large apertures between F 1.4 - F 3.5, have a very shallow or short depth of field. Small apertures on the other hand (between F 9 - F22), have a very long depth of field, making more things in focus in front of or behind the subject.
The closer the camera is to the subject, the more exaggerated the blurred look will be.