Ok so that last page WAS a shitpost. But what's a shitpost? What even is a meme? Well friend, here's a quick rundown...

Firstly there were image macros, appearing on the web in the early 2000s. The term originates from the Goons at the Something Awful Forums (founded 1999). Image macros were basically quick scripts that were ran by text entered into a forum post that was automatically formatted into a set of text, on an image. A text-macro that produced images.
This terminology would carry onto similar forums such as ResetEra and notably Facepunch (and eventually its successor Knockout.Chat), though none of these places actually had the applicable macros, and rather the same images were generated with photo manipulation tools (and later web hosted generators).

Posting an image macro in a thread in a way that was contrarian, inflammatory or de-railing was considered shitposting. These images began to spread, birthing what some colloquially refer to as 'classic' memes.

Shitposting survives as a term used in a non-forum context, and instead has been adopted by the various chans and other communities to be used to refer to posting memes, or 'shit' memes, etc. It exact meaning depends on the context on which it is used, but you can safely bet that 90% of the time it means "posting a meme(s)"

Memes are, in the current year and years past presently exist as a means to communicate ideas and jokes and many other things, ranging from "haha funny frog" to "haha funny racism" to things such as 'wholesome memes' which are designed to solicit an empathetic or 'feels good' response.
Memes are just, at this point basically any image with any sort of punchline or overloaded meaning (and it can range from absolute 'haha funny is random' style humor to serious commentary on world affairs presented in a more digestable format, eg a popular meme format) be it a reference to culture past, or relevant media. Even cropped Tweets count as memes with no additional context!

With that said, and as said previously, memes can basically be anything! Sometimes just something someone says can be accussed of being a shitpost. Context is everything yo! Be careful out there on the web, its a content tornado.