Sorry, got tied up there and didn't finish.
The other duty of a Line Check Airman is OE. When a pilot is hired at a major airline in the States, they will get a week of class in "Basic Indoc." It covers how the company operates, an afternoon of HazMat, De-icing, regulations, etc. Then there will be 3 weeks talking about the airplane they are going to be flying. Then there is an oral test over the plane they will be flying. Normally one of the longer two hour periods in your life. Then you move off to the sim for a couple weeks. Then there is a checkride. After that there may be more training for CAT II/III approaches or Class II Nav. Finally, after a couple months in the schoolhouse, they'll see a real plane. And it will be with people getting onboard or cargo being loaded.
The LCA watches over the new pilot during OE, normally 25 hours but it depends on the type of plane and if they've never flown for the airline before, or are moving from one type airplane to another or upgrading from the right seat to Captain. They were officially quailified when they passed their checkride. But really, when do you go out and stall a passenger jet or do steep turns? When do you shoot four approaches, lose a couple engines, miss and have a flight control malfunction, all in a couple hours? The sim training can turn out to be negative training because it is time compressed. Nice, relaxed briefings go out the window and become "109.5, 045 inbound, start at 1500 down to 213, same as we did a couple minutes ago." The LCA helps the new pilot apply the skills they learned in the schoolhouse to the real world. They are chosen because they know the company standards and SOPs, usually have some instructional background and it helps if they are very, very patient.
Varigflier, while most of us still say IOE for that time a new pilot has a babysitter, the current term is just OE. Just like the FAA is going to the term "Check Pilot" and not "Check Airman."