There are five main types of weed control that can be used in a residential or commercial landscape. It's important to note that some methods overlap, for example, a pre-emergent method may also be chemical in nature. 

1. Pre-Emergent

Any treatment that targets weeds before the seeds germinate and begin to grow is considered a pre-emergent treatment. Chemical pre-emergency herbicides can be applied to the soil surface or worked into the top few inches of soil, for example. Solarization is another pre-emergent method, but this entails tilling up the soil to expose weed seeds and then covering the site with clear plastic so that the seeds are cooked and killed by the heat of the sun. 

2. Preventative

 A preventive treatment is generally regarded as a non-chemical method that prevents weeds from encroaching into an area in the first place. A heavy mulch layer that suppresses weed growth is considered preventative. Planting dense grass or a heavy ground cover so weeds can't penetrate into a lawn or bed is also preventative. Another preventative method is installing edging around beds so weed roots can't grow into the bedding area.

3. Mechanical

Using tools or hand pulling to eradicate weeds are examples of mechanical weed control. This can be as simple as pulling up young weeds as soon as you see them or digging out deep tap roots with a trowel. Cultivators, tillers, and plows are also mechanical methods for controlling weeds, although these are usually reserved for use in garden beds or in areas that have yet to be seeded for a lawn.

4. Chemical

Chemical treatments use herbicides to target weeds. A full spectrum herbicide kills every type of plant, from lawn grasses to weeds. Targeted herbicides, such as broadleaf solutions, only kill the type of plants listed on the label. Pre-emergent herbicides also fall under the chemical weed control umbrella. Application time does matter and will be listed on the label. Methodology is also important. For example, full spectrum herbicides are applied with targeted sprays, while a broadleaf herbicides may be broadcast over an entire area.

5. Biological

Biological controls are less common in residential applications, but they may be used in commercial or agricultural areas. For examples, using goats to clear brush is considered a biological weed control. In residential areas, chickens are sometimes used to clear garden beds of both weeds and insect pests before planting. 

Contact a professional weed control service if you aren't sure which method or combination of methods is best for your landscaping.