I have had astigmatism for as long as I remember, but I didn't get my first set of glasses and wasn't diagnosed till I was in Jr high. Before then my family just called me "Squinty Joe" but no one ever thought to take me to a damn optometrist
Bifocals. The most common type of multifocal. The lens is split into two sections. The upper part helps with distance vision. The lower half is for near vision. They’re usually prescribed for people over 40 who can’t focus well anymore. That’s due to presbyopia, an age-related change that affects your eye's lens.
Trifocals. These are bifocals with a third section. It sits above the bifocal portion of the lens. You look through it to see objects within arm's reach, like a computer screen.
There are also progressive lenses, which have no line, and start with your distance prescription at the top and progressively move towards your full reading prescription at the very bottom.
Yeah, I get "tri" and the denotative meaning of "trifocal", but honestly there's something wonkey about the lenses I have. I don't need any glasses to see stuff at arms reach, reading menus at a restaurant is no problem, but reading the fine-print at the bottom "may contain nut allergens" is difficult and reading the specials on the far wall is a fuzzy problem.