In the modern periodic table, rows are known as the periods, which indicate the last electronic layer of an atom.
Columns are groups, which indicate the number of atoms in the last electronic layer.
Groups involve elements with similar properties, such as metals, non metals, actinides and lanthanides, halogens, noble gases, among others.
Blocks make reference to the orbitals in which the electron configuration end for each atom, those are s, p, d and f.