A Force is push/pull upon an object resulting that object to interact with another object.
The Effects of Force are 
Change in shape of object
Moves the object which is in rest
Stops the object which is in motion
Accelerates the object
Deccelerate the object.

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Force is an agent whose action can(or can't) produce acceleration in a body. In the reference of Mathematically we can say it is the product of mass and acceleration of the body. It is denoted by 'F'(In your level or class, in higher classes you will see the arrow on symbol 'F' because it is a vector quantity, means acceleration have direction too so it is vector quantity).

Effects of Force:
1. It can start or teds to start motion.
2. It can stop or tends to stop the motion.
3. It can change or tends to change the direction of the motion and shape and size of an body or object.