Re: please tell me, are all stars formed in the same way , thanks !

Star formation is very complicated.  Stars form out of the stuff that 
exists between the stars (gas and very small solid grains of rocks and 
metals) usually in regions where lots of this material exists.  
Astronomers call these regions Giant Molecular Clouds. Often stars 
form in groups (clusters) out of these clouds.  Star formation appears to 
be triggered by shock waves that hit the Giant Molecular Cloud. It is 
possible that stars form as single stars rather than in groups.  But those 
stars are very hard to detect, so astronomers don't know too much about 
that type of star formation.

If you want more information, I can give you more details on the character 
of the Giant Molecular clouds and on what can produce shock waves in space.

Most of this information can be found in Introductory Astronomy books such 
as:  Foundations of Astronomy by M. Seeds.
[Moderator's note: you might also want to check out "Star Factories: the Birth
of Stars and Planets", a new book by R. Jayawardhana.]