"Just use the photo from the website for our brochure"

Have you ever downloaded an image from the internet and then printed it, only to get results that were, well, less than you expected? The image looked great on your computer screen, but when you printed it, it either printed at the size of a postage stamp or it printed at a decent size but looked blurry and/or "blocky"? The culprit is image resolution.
So what can you do to make photos you download off the internet appear just as high quality when printed as photos you took yourself with your digital camera? The answer - ABSOLUTELY NOTHING. There simply are not enough pixels in most internet images to allow them to print at high quality, without printing them at the size of a postage stamp.
Let me explain why:

A simple arithmetic will calculate the size in inches for:
Screen:         640 pixels / 72 pixels/inch = 8.88 inches
Print:            640 pixels / 300 pixels/inch = 2.13 inches

LOW-RESOLUTION PHOTO SUITABLE FOR INTERNET

SAME LOW-RESOLUTION PHOTO ENLARGED FOR PRINT (see the pixilation)

ORIGINAL HI-RESOLUTION PHOTO SUITABLE FOR PRINT

Conclusion: the same 8.88” photo that looks good on you monitor will print only 2.13” at the same quality. Any attempt to stretch that photo will result in pixilation, meaning you will try to “add” pixels that the original never had.
Of course, there much more to add on this chapter, but now you have at least a pretty good idea of how resolution works.