Friends:

Jhãna is the 1^st Mental Absorption!
Jhāna is Pāli: In Sanskrit = Dhyāna, in Chinese = Chān, in Japanese = Zen. 

Preliminaries:
Purified Morality => Clear Conscience, innocence and the mental elation thereof.
Guarding the Senses => Absence of Temptation, greed, desire, and attraction.
Clear Comprehension => Acute Awareness and absolute and acute mental presence.
Contentment => Calm and stilled satisfaction even with nothing. Joy and Happiness. 

Mental Factors of Entry:
1: Absence of any Urge of Desire.
2: Absence of any Aversion or Anger.
3: Absence of any Lethargy and Laziness.
4: Absence of any Restlessness and Regret.
5: Absence of any Doubt and Uncertainty.
1: Presence of Directed Thought.
2: Presence of Sustained Thinking.
3: Presence of Rapturous Joy.
4: Presence of Pleasurable Bliss.
5: Presence of Single-Pointed Focus.

Subjective Experience:
Intense presence and awareness. Effortless, undistracted, and focused thinking.
Attention anchored even at ease at any chosen object. Mind is fixed and unified.
Final end-result of chain of reasoning is always reached quickly and successfully.
Body is without any pain and is felt like being a feather inside a big empty silent hall.
There is joy, bliss and happiness mixed into solid calm just like a smiling mountain! 

Stages:
1: Directing (adverting to sign of serenity).
2: Attaining entrance and stabilizing that.
3: Prolonging and controlling duration.
4: Emergence from absorption.
5: Reviewing (looking back on). 

Grades:
I:  Access Concentration like in the neighbourhood and approaching (upacāra-samādhi).
II: Full Absorption Concentration fixed and anchored on object (appanā-samādhi). 

The meditation techniques which can induce Jhāna Absorption are:
Awareness of Breathing (Ānāpānasati)
Basic Entirety Object (Kasina)
Inner Organs and Corpses (Kāyagatāsati)
The 4 Infinite and Divine States (brahma-vihāra)
The 4 Formless States (Āruppa) 

Manual:
The Path of Purification: Visuddhimagga.
By the Great Explainer: Buddhaghosa. 5th century AC. Ceylon.
http://what-buddha-said.net/library/pdfs/PathofPurification2011.pdf

Buddha Said:
Having momentarily eliminated the five mental hindrances of: Sense Desire, Ill Will,
Lethargy and Laziness, Restlessness and Regret, and Doubt and Uncertainty, which all
are defiling imperfections of the mind that obstruct concentration and understanding,
quite secluded from sensual pleasures, separated from disadvantageous mental states,
one enters and dwells in the first Jhāna absorption of directed and sustained thought
joined with joy and pleasure born of secluded solitude. One makes this joy and pleasure
born of secluded solitude pervade, perfuse and fill the entire body so that all parts is
thrilled by this joy and pleasure born of secluded solitude. Even as a clever barber or
his apprentice would put soap powder in a brass basin, sprinkle it with water, gradually
knead and moist it into a ball of foam soaked thoroughly everywhere inside out yet
without dripping, so too does he pervade, perfuse and fill his entire body so that all
parts is completely drenched with joy and pleasure born of secluded solitude.

More on Jhāna absorption:
http://What-Buddha-Said.net/drops/Details_of_the_Jhana_Absorptions.htm
http://What-Buddha-Said.net/drops/Requisites_for_Jhana_Absorption.htm
http://What-Buddha-Said.net/drops/What_is_Right_Concentration.htm
http://What-Buddha-Said.net/drops/III/Concentration_Samadhi.htm
http://What-Buddha-Said.net/library/DPPN/wtb/g_m/jhaana.htm
http://What-Buddha-Said.net/drops/Samma-Samadhi.htm

Soaked in Jhana Joy!

Have a nice & noble day!

Friendship is the Greatest!
Bhikkhu Samāhita _/\_ ]
http://What-Buddha-Said.net