If you were not aware, you can get context sensitive help on almost all dialogs and PropertyManagers in SolidWorks by hitting F1 (or pressing the Help button in the dialog) while the dialog is up. For the options dialog, it will bring up a help topic for the specific page of the Options dialog that you are on. In this case, the following help topic:
Then you can scroll down to the option description for the item you are interested in.
In this case, the option is simply to turn off the horizontal/vertical guide lines that SolidWorks gives to you when creating or dragging notes and dimensions. These guide lines help users align notes and dimensions if desired, and the option allows those guide lines to be turned off if you don't use them or find them intrusive.
I hope this helps,
Disable note/dimension inference. If cleared, when you place a note or dimension, a line appears to indicate horizontal or vertical alignment with other notes or dimensions.