Loam refers to the texture of soil and further, an even mix of sand, silt and clay. A soil with a nice loam will retain moisture and nutrients whilst also draining properly. Soils with heavy clay, for instance like the one pictured here, tend to be a heavier loam that hold on to water. If a soil is predominantly sandy, water will drain too quickly, as the particles are larger.
A soil with a perfect loam can be achieved over several years with the addition of compost and the consistent working and tilling of the soil. You should also work to steer clear of a compacted loam by refraining from walking on any garden beds.