what is the use of "used" in this sentence?

I want to know the difference between these two sentences.

1. 
   

   I used to go by bus to school.

   
   


2. 
   

   I go by bus to school.

   
   

In the first sentence is it necessary to use the word used?

Thanks in Advance.

Answer

1. 
   

   I used to go to school by bus.

   
   


2. 
   

   I go to school by bus.

   
   

The first sentence is in the past, where the second one is in the present.

You use "used to" + infinitive to refer to something that happened regularly in the past, but no longer happens in the present. You went to school regularly by bus in the past, but you don't do so now. Maybe you go by car now.

The second sentence in the present simple indicates that it's routine or regular for you to go to school by bus in the present.