Definition
Truth conditions are the factors that have to apply in the real world in order for a statement to be considered either true or false. In other words, truth conditions support and determine the truth value of a given sentence.
Typically the meaning of a sentence determines its truth conditions. (Kroeger, 2019, p. 36)
Examples
The truth conditions in the first example below depend on John being the individual being discussed and that John must be moving in a walking fashion.
The truth conditions in the second example below depend on the speaker having a dog and that their dog is not present at the statement’s moment of utterance.
The truth conditions in the third example below depend on John being the individual of discussion and that John must no longer be present at the statement’s moment of utterance.



References
Suttles, W. (2004). Musqueum reference grammar. UBC Press. SFU Student Access.