This refers to countertops made with acrylic and resin, which are scratch-resistant. The opposite of “solid surface” is “porous surface,” with materials such as marble and soapstone.
Solid surface countertops are not just scratch resistant, but also resistant to bacteria and mildew so this is a popular choice in bathroom vanities. This material is available in a variety of colors; some can mimic the appearance of luxurious materials, but not the texture. The only caution with their material is that it cannot withstand high temperatures, so hot items can potentially damage the surface. However, the damage can be sanded away to fix it.