Importing data to Mathematica from Excel sheet and DAT files

How to import data from Excel sheets and .dat files? Mathematica, exporting data, importing data, plotting with Mathematica, Excel sheets, Excel data dat files, Mathematica tutorials, Mathematica for students, Mathematica for beginners, Lists in Mathematica, 2d plotting in Mathematica, 3D plotting in Mathematica, #Mathematica #equations #data #excel #dat