Mold testing or sampling can be done for one or more reasons. One reason can be to find out what your family is being exposed to inside your home which can be useful for those more affected by mold than others especially with health conditions that can be exacerbated by exposure to mold and mold spores such as a person having asthma.
This is done with a machine that pumps air through a 'cassette' which captures particles in the air like mold spores, pollen and rusts. These cassettes have a 'sticky' paper inside like fly paper where the particles get stuck and then is analyzed at a lab which identifies the various mold spore types and how many are present. When air sampling is done for a house or condo air samples are taken in one or more areas of the home and then at least one outside sample for comparison. The industry guidelines for an acceptable or normal inside air sample of mold spores is when the number and type of mold spores is similar in number and type to the outside sample.
This is exactly what it sounds like. One way to confirm if mold is present on a surface is by using what is called a 'tape lift' sample where special clear tape is used to pull particles off the selected surface and is analyzed at the lab identifying what types of mold are there.