These two words are terrible shorthand for a process that Garcia uses ten pages of text to describe. It is on page 410 of his 1855 presentation that he summates the information that we singers need to be most interested in.
Of the Qualities of the Voice.
Various simultaneous causes modify the qualities of the voice: 1. according as the glottis partially or entirely closes the passage between the explosions, it produces veiled or brilliant sounds;
If you take the time to read the full text from which I extract the above quote, you should come away with a new respect for the larynx.
Complete Glottal Closure
Incomplete Glottal Closure
