Smart Guides as they are called, smartly guide you while you move around your screen creating or manipulating objects on your artboard. They create temporary snap-to guides that help you align and/or modify objects relative to other objects.

Smart Guides are on by default. To toggle Smart Guides, go to View > Smart Guides or Ctrl + U (Windows) and Command + U (Mac). Smart Guides are shown in light green color by default, but you can change their color in the ‘Smart Guide Preferences’ window. To open the Preferences window, do either of the following:

a. For Windows: Edit > Preferences > Smart Guides… For Mac: Illustrator > Preferences > Smart Guides.

b. On the Application bar (below the Menu bar) click on ‘Preferences’ button.

In the Preferences window, from the drop down choose ‘Smart Guides’.

Let us take a look at each of these options in detail;

1. Color: Specifies the color of the guides. Use the drop down to choose a new color from the list.

2. Adobe Illustrator displays six kinds of Smart Guides;

(i) Alignment Guides:

(ii) Anchor/Path Labels:

They identify the anchor points and paths as you hover your mouse over them.

(iii) Object Highlighting:

The objects that have live effects or distorts applied to them, are highlighted with Object Highlighting.

(iv) Measurement Labels:

When you draw or modify objects using various Drawing Tools and Text tools, Measurement labels display small labels with the object’s dimensions. While the Measurement Labels display the dimensions as you draw, they also display an anchor point’s X and Y coordinates from the object’s original location, when you move the objects.

(v) Transform Tools:

Transform Tools display information as you scale, rotate or shear objects.

(vi) Construction Guides:

Construction Guides will display guidelines as you draw new objects. You can specify as many as six angles at which you would like Illustrator to draw guidelines drawn from anchor points of a nearby object. Choose angles from the drop down or enter Custom Angle values in the boxes.

3. Snapping Tolerance: Specifies the number of points the pointer must be placed from another object for Smart Guides to take effect.

If you are not using Smart Guides yet, I would suggest you to start using them. I hope you liked the tutorial and I thank you for viewing it.