To understand any process you must clear all your basic first.I will not go in details for that but you can go through your chemistry textbook.Normally  all reactions have functional groups,bonds,and other factors to are plays main role in any chemical reaction.

We begin by defining some basic terms that will be used frequently as this subject is elaborated. Chemical Reaction: A transformation resulting in a change of composition, constitution and/or configuration of a compound.

Reactant or Substrate :

 The organic compound undergoing change in a chemical reaction. Other compounds may also be involved, and common reactive partners (reagents) may be identified.

The reactant :

 It is often (but not always) the larger and more complex molecule in the reacting system. Most (or all) of the reactant molecule is normally incorporated as part of the product molecule.

Reagent :

 It is a common partner of the reactant in many chemical reactions. It may be organic or inorganic; small or large; gas, liquid or solid. The portion of a reagent that ends up being incorporated in the product may range from all to very little or none.

Product :

 It is final form obtained by the reactants in a reaction.

Reaction Conditions :

 The environmental conditions, such as temperature, pressure, catalysts & solvent, under which a reaction progresses optimally. Catalysts are substances that accelerate the rate ( velocity) of a chemical reaction without themselves being consumed or appearing as part of the reaction product. Catalysts do not change equilibrium positions.

Generally any chemical reaction will be written as :

Reactan (s) + Reagent (s) ---> Product (s)                
 { depending upon what the reaction condition kept }

Now check the different types of any Chemical Reaction.

1.Combustion Reaction :


A combustion reaction occurs when stuff burns that means it take place when a compound containing carbon and hydrogen reacts with oxygen to make water vapour, carbon dioxide, and heat.

General Example can be :

C?H?  + O2 ----------->  CO2 + H2O

Means any compund containing carbon and Hydrogen reacts with Oxygen under appropriate conditions produces carbon dioxide and water with large amount of heat.

Just see the example as below :

C6H12 +9O2   -----------------> 6CO2 + 6H2O 

2.Synthesis Reaction : 


When two or more compunds are mixed or reacted to produce a new molecule is known as synthetic reaction.This reaction were carried over a appropriate reaction conditions .
The General Example as below :

A + B --------->  C

An example we can take as :

2Na + Cl2 --------> 2 NaCl

3. Decomposition Reaction :


As the name denotes that decompose means something is breaks.In chemistry we can say after certain force the compound gets decomposes to give new products .

Take an General example as :

AB ----------> A + B

Example of such reactions is below :

2H2O ------------------> 2Hg + O2g          [electrolysis ]

2H2O2l      --- ---------> 2H3Ol + 2O2g       [ Unstable condition of Hydrogen peroxide in water }

H2CO3aq-------------->H2Ol+ Co2 g    ([ decomposition of carbonic acid,e.g. drinking a soda ]

4.Single Displacement Reaction :


Single displacement reaction, also called single replacement, is a reaction in which one element is substituted for another element in a compound.

General Example will be :
 A + BC ----> AB + C

These types of reactions mainly acts in Redox reaction.

A example of this reaction is :

Mg + 2HCl ------------> MgCl2 +  H2


5.Double Displacement reaction :


Also called a double “replacement” reaction, were two compounds swap components in other words we can say this reaction occurs when the cations of two chemical compounds switch places. The general form for this reaction is:

AB + CD ----> AC + BD

Example of this reaction 

HCl + NaOH ---------> NaCl + H2O

6.Acid Base Reaction :

As we know a compound which loos proton known as Acid and which accept proton known as Base.
This reactions are more popular and had unlimited applications with different combinations.
In this reactions we observe the Double displacement type reaction .
General Reaction we can give as :

HA + BOH -----------> AB + H2O

Here we can say when an equimolar amount of acid and base used it tends to Neutral otherwise a compound which is more it leads to Acidic or Basic condition.

Example of this reaction ;

HCl aq +NaOHaq ---------->  NaClsalt +H2Oaq


What we learn

Now,as per above reaction types what we obeserved and learned from it just in short ,

When any reaction written we can think in mind and solve the question by asking yourself as ;

If the reaction gives CO2,O2,H2O then it an Combusion reaction

If the reaction gives a complicated formation of compund it will be an Synthetic Reaction

If the a compund gives different new products it is an Decomposition Reaction

If the reaction gives pure unbond compund it is Single Displacement Reaction.

If the reaction forms water beacause of acid and base mixing it is an Acid Base Reaction

And if there is exchange in element/group between the reactiong compounds then it is Double Displacement Reaction.