Understanding of tuberculosis (TB) requires students to identify some critical points. The disease is caused by Mycobacterium tuberculosis, a peculiar bacterium mainly transmitted by inhaling infectious droplets expelled when coughing, talking and sneezing. One of the least understood aspects is that, following the exposure to the infectious droplets, a third of the people develop a latent pulmonary infection. The last means that some people control, rather than eliminate, the bacteria; therefore, some of them can later develop the TB disease, especially when they present an immunological deficiency. The key is to recognize the cell-mediated immunity as a determining factor in the course of the latent or active infection and that the antibodies, the complement system and the phagocytosis by non-activated macrophages result irrelevant in the defense against TB.Another major concern is the effect of multidrug resistant and extensively drug resistant strains. Management of multidrug resistant -TB and extensively drug resistant -TB is more complicated due the long treatment periods and the elevated costs.