Historically the altar is where people made sacrifices to commune with their Deity. In Freemasonry it is where masons, who commune with the Grand Architect of the Universe, can all together commune with deity.
A fellowcraft represents a modern workman at the building of King Solomon's Temple. the position the apron is in represented their level of experience.
A master mason is a modern representation of an Overseer during the construction of King Solomon's Temple. Workmen then had different positions of their aprons to represent their duties.
A Past Master of a lodge is someone who spent at least one year as Master of the lodge. It is different from the Master's symbol as it is more admonished.
The Secretary records the proceedings of all meetings, receives communications from outside of the lodge, and hands off money received to the Treasurer.