The explicit meaning of this advertisement is that there are too many cats and other animals in the animal shelter, and they lack space for them.
The implicit meaning is that this is not a good condition for the animals, and it arouses sympathy for them by using the picture. By eliciting an emotional response from you, it prompts you to adopt at least one of the cats.
Explicit is the facts but also feelings, so the cats are crowded so they may feel cramped or tight and uncomfortable, whereas internal is what you are feeling on the inside such as sad that they are in the shelter or mad that someone would leave them there exc
This is an example of an allusion , because the sentence is referring to an important political personality of the past (Socrates). The writer wants to underline the importance of Socrates contribution to the academic freedom.
