How do single, double and triple covalent bonds differ?

Hint: Covalent bond is actually formed by equal sharing of electrons from the atoms which participate in the bond formation. The pair of electrons which are participating in this type of bonding are known as shared pairs or bonding pairs of electrons.

Complete answer:
Covalent bonds are also known by the name molecular bonds. The main difference between single, double and triple covalent bonds is based on the number of shared electrons. If only one pair of electrons are shared by an atom then it is known as single covalent bond which is represented by single bond i.e. $C-C$ and single bonds have greater bond length as compared to double or triple bonds.
If two pair of electrons are shared by an atoms then it is known by the name double covalent bond which is represented by double bond i.e. $C=C$ and double bond have moderate bond length i.e. greater than triple bond but lesser than single bond and if three pairs of electrons i.e. 6 electrons are shared between the atoms then that bond is known as triple bond which can be represented as $C\equiv C$ and bond length of triple bond is low.

Note: The reactivity also tells us the difference between the three as single bond atoms are less reactive, double bond atoms are moderately reactive i.e. more reactive than single bond but less reactive than triple bond and triple bond is highly reactive as compared to both.