What does "less hindered hydrogen" mean? In a book they have given a statement,


  In the process of pyrolysis of esters, esters having  beta hydrogen are heated at high temperature and then alkenes are formed along with carboxylic acid.
  If there are two beta hydrogens then beta hydrogen having less hindrance will participate in the reaction.


In the last line, what do they mean by less hindered hydrogen?
Consider these following two structures from the same compound:



The two Newman projections are along the horizontal $\ce{C-C}$ bond which is, of course, freely rotatable. The two structures represent two possible syn-elimination transition states. Note that in the left-hand structure there is a steric clash between the tert-butyl group and the methyl group. The right-hand structure has no such clash. It is therefore the preferred transition state for this reaction.

‘Less hindered hydrogen’ basically means that hydrogen that leads to the more stable transition state.