Question: In my text book they said that:

> 
> 1. If no resultant force acts on an object, it will not accelerate; **it will remain at rest or it will** **continue to move at constant speed**
> 2. If an object is at rest or is moving at a constant speed in a straight line ,we can say that there is no resultant force on it.
> 
> 
> 

Now my question as it concentrates more on the first point.

How if the resultant forces or force are zero still the object moves at a constant speed and some times it does not move (or it is at rest as they say)?

Answer: 
A small and simple analogy to get the basic insight:

If each month, you spent as much as you earn, you will have constant savings.
If you started without savings, you will continue to have zero savings. 
If you started with \$1000, it will remain \$1000. In short: with net revenue zero, your savings are constant. Change revenue in force and savings in velocity, and you get what you need.
You might be confusing with pushing an object forward to maintain its motion.

For example, we pushed a CART forward and we got to maintain pushing it to keep it moving forever. Then, when we let go it will stop.

This is just because there is friction, this friction will cause the cart to stop, remove that and the cart will move forever! In real life Earth scenario however, this seldom happens, but push a cart in outer space and viola! It says goodbye us!