You can lay out a quick flier in Microsoft Word, Excel, or PowerPoint, but real page layout software allows for high-quality printing and greater flexibility in your layout to achieve the best visual communication and hierarchy possible when communicating. Standard page layout programs include CorelDRAW and InDesign, but Adobe Illustrator or Adobe Photoshop are more well-known (and offer a wider range of use) than InDesign.
Adobe Illustrator and CorelDRAW are vector-based programs and can handle limited editing of photos/images, while Adobe Photoshop is bitmap-based and can handle either vector (resizing, layering up, and some color changing) or bitmap editing. The other programs include setting up the margin and bleed areas, as well as allow for crop or trim marks, while Photoshop can do these things if you put it in yourself and account for it. If your goal is to do a single page layout (flier, poster, etc.) then CorelDRAW or Adobe Illustrator are just the trick for your layout needs.
Information courtesy Jennifer Foy, Unisub