Phage lambda is a type of bacteriophage, which is a virus that specifically infects bacteria. It is commonly studied in molecular biology due to its simple structure and ability to integrate its DNA into the host bacterium's genome. This integration allows it to enter a dormant state, known as the lysogenic cycle, where it can replicate along with the host's DNA. When conditions are favorable, phage lambda can switch to the lytic cycle, where it actively replicates and produces new virus particles. This process ultimately leads to the lysis, or destruction, of the host bacterium, releasing the new phages to infect other bacteria.