try+gerund/infinitive (Difference in meaning)

1. 
   

   I tried to open the door.

   
   



2. 
   

   I tried opening the door

   
   

We can use both infinitive and gerund with verb "try" as used in above sentences. Does it change the meaning of the sentence if use gerund or infinitive?.(here i don't know if the meaning of sentences is changed.)

The same confusion arise in these two sentences. 1.I stopped seeing him. 2. I stopped to see him.(But in case of these two sentence i know the meaning is changed but don't know exactly what the change is).