Right effort and concentration I was reading about the noble eightfold path and Right effort, thought and concentration, they seem to be very similar. What are the differences?
Right Efforts is about removing unwholesome states and cultivating wholesome states. Right Concentration deals with developing the Jhana as a means to displace certain subset of unwholesome states. Jhana is a wholesome state hence arousing Jhana can be viewed as applying efforts to abandon the 5 hindrances. This done through developing the Jhana factors. A mind with the Jhana factors aroused is wholesome. 

In short:


Abandoning hindrances and developing the Jhanas, Right Concentration, is a subset of Right Efforts hence the similarity
Right Effort deals with abandoning all unwholesome states and developing wholesome states, while Right Concentration deals with developing the Jahan, hence the difference


Right Effort


  (6) And what, bhikshus, is right effort?
  Here, bhikshus, a monk
  brings forth the desire for the non-arising of unarisen evil unwholesome states; he makes an effort,
  rouses energy, applies his mind, and strives;
  
  he brings forth the desire for the abandoning of arisen evil unwholesome states; he makes an effort,
  rouses energy, applies his mind, and strives;
  
  he brings forth the desire for the arising of unarisen wholesome states; he makes an effort, rouses
  energy, applies his mind, and strives;
  
  he brings forth the desire for the maintenance of arisen wholesome states, for their non-decay,
  increase, growth and fulfillment by cultivation; he makes an effort, rouses energy, applies his mind, and
  strives.
  
  This, bhikshus, is called right effort.


Right Concentration


  And what, bhikshus, is right samadhi [concentration]?
  Here, bhikshus,
  
  (1) a monk, detached from sensual pleasures, detached from unwholesome mental states,
  enters and remains in the first dhyana,
  accompanied by initial application and sustained application,
  accompanied by zest and happiness, born of detachment [ie born of samadhi].
  
  (2) With the stilling of initial application and sustained application,
  by gaining inner tranquillity and oneness of mind,
  he enters and remains in the second dhyana,
  free from initial application and sustained application,
  accompanied by zest and happiness born of samadhi.
  
  (3) With the fading away of zest, he remains equanimous,
  mindful and clearly knowing,
  and experiences happiness with the body,
  he enters and remains in the third dhyana,
  of which the noble ones declare,
  ‘Happily he dwells in equanimity and mindfulness.’
  
  (4) With the abandoning of pleasure and pain—
  and with the earlier disappearance of joy and grief—
  he enters and abides in the fourth dhyana, 
  that is neither pleasant nor painful,
  with a mindfulness fully purified by equanimity.
  This, bhikshus, is called right samadhi.


(Magga) Vibhaṅga Sutta also in Sacca Vibhanga Sutta