By definition, loamy soils are friable, possessing a mixture of clay, sand, and humus (and/or silt) that is ideal for growing plants. While those new to gardening and landscaping are probably familiar with terms such as "clay" and "sand," they may well be unfamiliar with "humus," so let's gain a better understanding of the meaning of that word before proceeding.
Humus is organic matter partly or wholly decomposed. When the decomposition is hastened by human intervention in order to use it as a soil amendment, it is virtually synonymous with "compost." A generous admixture of this organic matter to soil can help make it more friable.
What's the Big Deal About Loam?
Why are gardeners and landscapers so in love with loam? The answer is easy to understand if you consider the alternatives. For example, a soil with too much sand in it is too porous. Water runs through it as if running through a sieve. What is the result of this porosity? Needed water percolates right past the root systems of your plants. It does not hang around long enough for them to drink it up.
On the other hand, a soil with too much clay in it does not drain sufficiently well. So you have the opposite problem: Excess water hangs around too long and rots the roots of your plants. Another problem with overly clayey soils is often compaction, one solution to which is working some loam into the ground in question.
The Problem of Compacted Soil
Compacted soil is a big enough and common enough problem to warrant a closer look. "Compacted" is a term applied to soil which, deprived of proper aeration (perhaps due to heavy foot traffic, among other factors), suffers from excessive water runoff and poor conditions for plant rooting.
How do you solve the problem of compacted soil? In a lawn, you can correct the problem mechanically through core aeration. When opening up a new garden, people often employ garden tillers to break up compacted soil in conjunction with introducing loam and soil amendments. Earthworms can help you avoid a recurrence of compacted soil.
Another use for the word "compaction" in a horticultural context regards making compost, where compaction occurs under anaerobic conditions. Turning a compost pile frequently is one way to avoid such compaction.
Having Loam Delivered to Your Property
People who are not lucky enough to inherit a property rich in loam often buy it, having a truck deliver a load (priced in cubic feet). But be careful that the load does not contain the rhizomes of an invasive weed such as Japanese knotweed. One suspects that loam deliveries have been largely responsible for the spread of this terrible weed over the years. As if to prove the point, the soil-moving business shown in the picture above sports a thriving colony of Japanese knotweed right in front of its own establishment.
Acquiring loamy soil in this manner can become quite expensive if you are attempting to cover large areas with it. One compromise is to garden with raised beds. These structures come in many shapes and sizes. A great virtue of a raised bed is that you do not have to bend over to weed it.