You need to know the difference between a non-selective and a selective herbicide before you perform or authorize any herbicide application on your property.
A non-selective herbicide kills all actively growing vegetation by contact or by a systemic mode of action (chemical transported throughout plant). As an example Round-Up (Glyphosate) is commonly used to kill all existing unwanted vegetation growing in a poorly maintained landscaped area before planting or installing desirable seed or mature plants shortly after. Residual weed control (pre-emergent herbicide, soil sterilants, etc.) should be considered when choosing the correct non-selective herbicide needed for a particular site specific vegetation control task at hand.
A selective herbicide kills only certain target plants (as specified on product label) and leaves behind all other plants virtually unscathed (dosage and timing of application dependent). Most selective herbicides used on turf (in particular) are systemic in nature (chemical transported throughout plant).
A decision will need to be made if only a select few unwanted broadleaf weeds, grasses, vines, etc. need to be eliminated or if everything growing in a particular target area will need to be controlled.
As always, please consult an industry professional for proper target plant identification and best available control options (organic, synthetic, contact, systemic, dosage, mechanical, cultural, etc.) before any/all pesticide applications are performed.