In general, an estimator is responsible for understanding the blueprints, being able to pick the needed items required from the blueprints, and formulate a materials list to price. He would then need to be able to attach labor hours to specific tasks, and procure equipment costs, in an effort to be able to come up with comprhensive cost to install a specific project.
Since there is a training program, I assume this is a larger company with an estimating department. If so, you may be trained in how to use quickpen, or other estimating software, which makes life easier, but either way, you got a lot to learn.
Your job will entail looking over a lot of different plans. It is a job that some guys love while others hate it. It really depends upon your makeup, if you like doing this detail oriented type stuff. One thing about it, estimators usually arent out on a cold roof in winter, or a hot one in summer. Another thing is the estimator is usually a brunt of wisecracks, as in "we lost money on this job, its the estimators fault". its kindof a thankless job, like most in this business, but it can pay the mortgage just fine.