Wikipedia article on TED (conference): "TED (Technology, Entertainment, Design) is a global set of conferences run by the private non-profit Sapling Foundation, under the slogan "Ideas Worth Spreading". TED was founded in 1984 as a one-off event; the annual conference series began in 1990. TED's early emphasis was technology and design, consistent with its Silicon Valley origins, but it has since broadened its focus to include talks on many scientific, cultural and academic topics."
The structural concept of portuguese preps are a little different from english. If you would literally translate "at" you would get "em", which in portuguese doesnt make any sense. Think it like "laugh of sth" and "yell with sth" While it can sound pretty weird in english, it makes perfect sense in portuguese.
But this indeed has some confusion: "rir com" means that you are laughing together with someone, while "gritar com" can perfectly mean the same, but it is very rare to see it being put that way.