The simplest way to think about this kind of yard construction is anything which involves covering the upper layer of soil. This kind of work is especially common in urban areas where grass and plants are not abundant or do not grow well - as a result, professional contractors offer man-made ways to help improve the look of your home's front or backyard.
Some of the most common small hardscape projects include patio stones, sidewalks and retaining walls. Patio stones are the simplest form and can vary from a single line of stones to interlocking courses in multiple colors or patterns. Sidewalks, meanwhile, may be hand-placed stones or poured asphalt or concrete. Retaining walls typically involve courses of brick or stone laid on top of one another to form a barrier between hardscapes and "softscapes" such as gardens, trees or lawns. Constructed correctly, these walls allow water to drain properly, keeping as much as possible on the softscape while preventing it from running under (and therefore eroding) hardscaped features. Larger hardscape projects can include concrete or wooden decks or large vertical features which wouldn't be possible if placed directly on soil.
Water is an important concern for any hardscape project, because in areas with little available bare earth, drainage must be a focus. If water pools on wooden or stone features it can erode them over time or may cause backups in local sewer systems. Reputable hardscapers should design a specific plan to drain your deck, walkway or patio.