Hint:- These lines are widely observed in day to day scenarios and are very familiar phenomena. They are observed in the processes like dispersion, related to sunlight. Firstly we need to give a history behind it as the name comes from the English physicist Joseph von Fraunhofer. They are of various varieties and nearly $25,000$ of those.
Complete step-by-step solution: Fraunhofer lines are a band of special absorption lines. They are named after Joseph von Fraunhofer, a German Physicist. These sets of lines were originally observed in the optical spectrum of the sun. They are told to be first observed by an English physicist William Hyde Wollaston in $1802$ . Since $1814$ Fraunhofer experimented heavily over them and plotted more than $500$ Fraunhofer lines. He also assigned them brightest by letters A to G, which is still in use today. There are $25,000$ Fraunhofer lines known till now. We can observe a set of visible spectrum when sunlight is passed through the prism. This spectrum obtained is famously known as Fraunhofer Spectrum. This is, of course, an absorption spectrum. The black lines, over $600$ of them, are due to the absorption of particular wavelengths of light by chemical elements in the outer layers of the Sun. This concludes that if we correctly observe the wavelength of these black lines then we would be able to identify the elements in the sun. This would prove conclusive in finding the correct elemental data of Sun.
Note:- The wavelengths should be measured by utter precision as a minor change will result in a colossal change in identification. This is a reason though they don’t get caught by the naked eye but there are nearly thousands of them in a single visible light beam.