The number of valance electron in hydrogen is one and it can hence bond with only one atom.
In case of chlorine,it has seven valence electrons and it needs only one electron to become stable.
So hydrogen and chlorine combines to from HCl.
Ionic bonds are formed when a nonmetal and a metal exchange electrons.
Covalent bonds are formed when electrons are shared between two nonmetals.
Here there is no possibility of ionic bond since no ions are formed.
Thus covalent compound is formed.
When atoms of different electro negativities form a bond it is called as Polar bond.
When atoms of similar electronegativities share electrons to form a covalent bond it is called as Non polar bond.
Here electronegativity of hydrogen is 2.2 and chlorine is 3.16.So we can observe different elctronegativity.
Hence the HCl has a polar covalent bond.