Whenever somebody tells you they are having some graphics designed they often don't tell you what type of graphics design they're getting done. There are actually two really distinct kinds of graphic design.
The main one type of graphic design is designed for use in advertising posters and billboards. This sort of graphic design takes a lot of focus on things like resolution. If your graphic design artwork doesn't use a high enough DPI, or dots per inch, then your graphics will not convert well when they're enlarged to anything bigger than a business card. If you are planning to be using your graphics for advertising posters and things like that then you need to inform your graphics designer. They are going to need to make sure that they use the correct colour scheme as most ink jet printers do not use the web standard RBG, or red blue green, because ink jet printers generally make use of CMYK, or cyan magenta yellow black, as these are the colours that the inkjet cartridges come in. But if your graphics are made in RBG chances are they may come out looking extremely different when they are printed using CMYK.
One other kind of graphic design is made for digital use. The most common of these is for the net on websites. If you're having this type of graphic design done then you'll get far lower resolution images as web-site designers do not like to make use of high res images. They require a great deal longer to load when a web site is opened up and those that are looking at web sites do not want to wait for pictures to load. They likewise have to be designed in RBG rather than CMYK as this is the encoding that most of your monitors make full use of. There are also some colours that don't look great when they are used in web sites as the RBG colour coding distorts the shades a bit. So if you are planning on using the graphics you're having designed for your website you will want to tell the graphics designer so that they can ensure that the image files are sufficiently small to load rapidly, usually under a hundred kilobytes, and are also done in the right colour format.
In a nutshell, there are two unique kinds of graphic design. The actual advertising, branding type and also the type which is used on the internet. Both types of graphic design have their own group of specifications. You cannot use graphics intended for web site content material upon marketing posters as the DPI will not be high enough and it will be in the incorrect color encoding for the ink jet printers to deal with so the colors will not come out quite right. You also can't make use of graphics that have been created for marketing on websites. The actual files are going to be too large and the colour coding is going to be wrong for the monitor to translate properly therefore the color is going to be altered. Fortunately it is easy to transform a marketing image to a web image as you can do a color conversion and reduce the DPI. The actual change of the internet image to and marketing picture is a lot more challenging.