When you use Snaps in Smartdraw, what you are essentially doing is allow Smartdraw to "snap" your graphics/text/walls to a grid. That is, if your wall is drawn close to a grid line, then Smartdraw will "snap" the wall to the nearest gridline.
Let's look at the snap and gridline options.
Click on the Page tab at the top of the screen. To the right of where you define and create layers is a menu that allows you to turn on/off the gridline and to also set snaps.
Here, the gridline is turned on. If you also put a check in the "Use Snaps" box in the menu, then any item you draw or place in your floorplan will automatically "snap" in line with one of the gridlines.
When to Use Snaps
Use snaps when you want to place block items like bookcases or chair, that you want to line up.
Use snaps if you want walls or doors to fit to specific dimensions.
When Not to Use Snaps
You will most likely not want to use snaps if you are placing text boxes, or even graphics. Without using snaps, it is much easier to center text and other items to improve the appearance of your final floorplan.