"Hardwired" refers to equipment that is directly connected via cable or wire. For example, a hardwired video camera sends a signal through a cable to its destination (VCR or monitor). The advantage of a "hardwired" system is that you can usually rely on having a strong, clear signal at your destination given you are using a reasonable high quality cable limited to a reasonable length. The disadvantage of a "hardwired" system is the need to run cable between your source (i.e., camera) and your destination (i.e., VCR or monitor). This can be cumbersome as well as costly in situations where you have to run between walls, streets and buildings. It's especially difficult to do so in a covert manner.