Files generated by IntelliJ (ie. _1.fdt, segments.gen)

Hello,
i could found any help about this point :

i use IntelliJ (community 10.5) for my Java EE project including a lots of maven modules.

Then it's like IntelliJ create his own file :
  - moduleName.iml (seems normal for me)
and
  - (one directory per package name)/ including the followwin files :
    _0.fdt
    _0.fdx
    _0.fnm
    _0.nrm
    _0.prx
    _0.tii
    _0.tis
    segments.gen
    segments_2

I dont know what are this generated files/directories for ?
Are they usefull ?
how could we remove them ?

any help appreciated
Regards
Brice