Someone care to explain to me how Giphy embeds/keywords work??? (TW: gif heavy post)

How do Giphy embeds work? I tried embedding the code of a gif I found online, but it was not displayed at all. If I only follow the instructions Imzy gives me and insert keywords in the markup, the results are unpredictable at best and outright weird at worst.

See my highly ridiculous examples here:

[/giphy Spock Kirk]

Spock Kirk

[/giphy Bill Shatner]

Bill Shatner

[/giphy Spock's brain]

Spock's brain

[/giphy stalactite dildo]

stalactite dildo

[/giphy pon farr]

pon farr

[/giphy Spock in heat]

Spock in heat

[/giphy Space Husbands]

Space Husbands