"Jhana is like a meditative absorption state? I've come across this term."
"[Jhanas are] distinctive meditative states of high concentration in which the mind becomes unified. [...] Jhana is often referred to as an absorption state, since the mind in Jhana is so deeply concentrated that it 'absorbs' into the meditation object."
Richard Sankman, The Experience of Samadhi
Yes. Jhana also corresponds to "right concentration" (samma samadhi) in the eightfold path (see SN 45.8).
"Like a barrier once broken you go onto the next barrier an so on an so on."
Yes. There are multiple jhanas. The canon describes a sequence of 4 Jhanas followed by 4 more states (in later commentaries, they are known respectively as Rūpajhānas and Arūpajhānas). The commentarial tradition also expanded on the states that precede the first Jhana (e.g. access concentration).
"Is this process a permanent effect on the mind or a temporary effect of the mind, Do you basically start over from stage 1 every time [?]"
It may affect the mind in many ways, but one doesn't really stays permanently absorbed in Jhana during day-to-day. Reaching a certain Jhana may not necessarily require going through previous jhanas (though it is emphatically advised to perfectly master them in sequence and develop stability instead of trying to "jump around").
"does your body ever become accustomed to it [?]"
I'm not aware of any body related issues associated with Jhana.
"do you have to constantly renew the Jahana over an over in order to progress?"
I'm not sure what you mean by "renew", but just like any training that requires repeated practice, mastering jhanas also requires effort and training, specially to reach deeper Jhana states.