When someone lets you know they are having some graphics created they frequently don't tell you what type of graphics design they are getting done. There are actually two very distinct kinds of graphic design.
The main one type of graphic design is for use in advertising posters and billboards. This sort of graphic design requires a lot of focus on things like resolution. If your graphic design art doesn't use a high enough DPI, or dots per inch, then your graphics will likely not convert nicely when they're enlarged to anything bigger than a business card. If you are going to be using your graphics for advertising posters and things such as that you will want to inform your own graphics designer. They will need to make sure that they use the correct color scheme since many ink jet printers don't use the web standard RBG, or even red blue green, because printers generally make use of CMYK, or cyan magenta yellow black, as these are the colours that the inkjet cartridges come in. If your graphics are designed in RBG chances are they may come out looking very different when they are printed using CMYK.
One other kind of graphic design is made for digital use. The most typical of these is for the net on websites. If you're having this type of graphic design done then you will get far lower resolution images because web-site designers do not like to make use of high resolution pictures. They will take a lot longer to load whenever a website is opened and people who are looking at websites don't want to wait for pictures to load. They likewise have to be developed in RBG instead of CMYK because this is the actual encoding that many of your monitors make use of. There are a few colors that don't look good when they're used in websites because the RBG colour coding distorts the colours a little. So if you're intending on making use of the images you are having designed on your web site then you need to inform the actual graphics designer so that they can make sure the image files are small enough to load quickly, generally below a hundred kilobytes, and are completed in the correct color format.
In short, there's two distinct types of graphic design. The advertising, branding kind and the kind that is used on the web. The two kinds of graphic design have their own set of requirements. You cannot make use of graphics meant for website content on advertising posters because the DPI won't be high enough and will also be in the wrong colour encoding for the printers to handle so the colours will not come out quite correct. Additionally you cannot use images which have been designed for advertising on websites. The documents will be too big and also the color coding will be incorrect for the monitor to interpret correctly therefore the colour will be distorted. Luckily you can easily change an advertising picture to a web picture as you can do a colour transformation and decrease the actual DPI. The transformation of a web picture to and advertising image is much more difficult.