Question

What kind of reaction is
C2H4+3O2=2CO2+2H2O

Answer 1

It is called a combustion reaction

In order for you to have a combustion reaction you have to have two things:
A hydrocarbon and an oxygen 

Answer 2

Explanation:

A chemical reaction in which a hydrocarbon reacts with oxygen atom and results in the formation of carbon dioxide and water is known as combustion reaction.

For example, $C_{2}H_{4} + 3O_{2} \rightarrow 2CO_{2} + 2H_{2}O$

Here, ethene is the hydrocarbon which is reacting with oxygen atom and yields carbon dioxide and water.

Therefore, we can conclude that the given reaction is a combustion reaction.