Resume summary
Also called professional summary, resume profile.
Two or three lines at the top of a resume stating what you do, at what level, and what you're aiming at.
The summary occupies the most valuable space on the page, so it has to do real work. What earns that space: your discipline and seniority, the domain you know, and one differentiator that's actually rare. What wastes it: adjectives. "Results-driven professional with a passion for excellence" tells a reader nothing they couldn't assume.
It is also the one place you can address something the rest of the document can't explain — a deliberate pivot, a return after time out, a relocation. One clear sentence there prevents a reader from inventing a worse explanation on their own.
The objective statement is its obsolete predecessor. An objective describes what you want from the employer; a summary describes what the employer gets. Only the second is useful to the person reading.
Master resume
A complete, unedited record of everything you've done, kept privately as the source you cut every real resume down from.
Resume tailoring
Rewriting an existing resume for one specific posting so the relevant experience is the visible experience.
Career gap
A period without formal employment on your work history — normal, common, and mostly a problem only when it's left unexplained.