D&D 5E - How does telepathy work?

I would think that, at its 'base' level, Telepathy would work just like speaking, save that it's only audible to the receiver. It's also a 'speech-dependent' ability, meaning that the recipient must have at least some form of language in order to work; by this, one could assume that pictures are not a part of the 'base' power. In other words, if you can create an effect with your voice, it should be also possible via Telepathy.

Psionicists (in other versions of D&D) who specialize in Telepathy CAN send images etc via their mind-links, much like Illusionists can summon visual images for the eyes.