***Not a teacher***
The first two are technical terms. The excerpt you have quoted is full of references to computer hard drive manufacture.
The drive functions by having rotating platters, which are very thin circular shaped magnetic disks, which spin very fast (several thousand revolutions per minute). Information is encoded onto the magnetic surface by passing an 'arm' across it. Data is read by a 'read head' and written by a 'write head'. You can check out some of the detail on wikipedia under the 'hard disk drive' article.
..therefore refers to the arm which moves just above the surface of the hard disk.Does "mechanical arms" refer to "arms of a robot"?
To say the read head rides above the surface means to hover. The arm is held a minute distance ("a hair's width') above the rapidly rotating surface of the disk platter and can therefore be thought of as 'riding across the surface' - even though it is the platter that is rotating. The arm is moved back and forth across the surface of the platter to access different parts.
I never got caught up in the typical business-executive kind of concerns.
This means I never got excessively involved with the sorts of things that a business executive would normally get involved with.
Student or Learner