The pulsating heat pipes (PHP), also called oscillating heat pipes, belong to the thermal system category of heat pipes, two-phase passive thermal devices used to transfer heat from a hot source to a cold region, with very high equivalent thermal conductivity, higher than any usual metallic material, light, and able to manage high heat fluxes. The PHPs add to standard two-phase passive systems the option to cover large surfaces, the very simple construction, the possibility to use very different materials and working fluids, the geometrical adaptability and flexibility. An a priori design of a PHP is still difficult, even if in the last years a better comprehension of the internal physical processes has led to accurate predictions of the experimental results. This chapter aims to offer an introduction to this intriguing topic, with a comprehensive list of the most important experimental results. The description of the fundamental processes in a PHP is only given in brief, and a detailed understanding is left to the following chapter on modeling and simulation. In order to help the reader to evaluate a possible design of a PHP, the influence of the different parameters and operation conditions is explained based on the results obtained by researchers in the last 15 years. Finally, promising potential applications of the PHPs are listed and categorized.