Venom: Let There Be Carnage, directed by Andy Serkis, also contained many references to previous Spider-Man films. The movie briefly explained further details about the symbiotes from Planet Klyntar and established how they reproduce to have offspring.
The second installment of Venom also established the universe in which the two movies take place. Furthermore, the post-credits scene revealed the origin of the character Venom and its future in the Sony X Marvel universe.
Venom 2 is based upon the Maximum Carnage comic series from 1993, while the first movie was based on the 1993's comic series titled Venom: Lethal Protector. Venom: Let There Be Carnage also established the symbiote's connection with the MCU and hinted at the potential involvement in Spider-Man: No Way Home.
How Venom already knew about the existence of the Multiverse
In the post-credit scene of Venom: Let There Be Carnage, Eddie and Venom are on the run after the events of the cathedral fight with Carnage and Kasady in San Francisco. The scene shows the duo refuging in a beach-side hotel, watching a Latin-American TV show.
Hive-Mind and Knull reference
While watching the show, Venom tells Eddie:
"80 billion light years of hive knowledge across universes would explode your tiny little brain."
In the comics, the symbiotes were created by an eldritch god of darkness named Knull, who preceded the Big Bang and existed in a void dimension called "The Abyss." The symbiotes processed a hive-mind which consisted of the collective knowledge of all symbiotes across time and space.
The hive-mind itself is a nexus controlled by Knull, and thus the knowledge includes "80 billion light years" worth of information. Here, the light-years refer to both time and distance.
How was Venom aware of the Multiverse and Peter Parker?
Likely, Peter Parker in Venom and Eddie's original universe might not be Spider-Man. So, the Sony X Marvel creative people could be hinting at retconning every Spider-Man project after the events of No Way Home.
In the scene, Venom and Eddie are transported to the main MCU, and their hotel room changes appearance. The TV plays a clip of the Daily Bugle's expose of Peter Parker being Spider-Man like we saw in the Spider-Man: Far From Home post-credit scene.
Venom then walks up to the TV and says, "That Guy," and licks Peter Parker's face on the TV. The scene insinuates that Venom is not too surprised to see this unknown vigilante. Furthermore, it hints that Venom might already be aware of Peter Parker's existence.
After establishing the Hive-Mind, it is plausible that Venom knows the symbiote in 2007's Sam Raimi-directed Spider-Man 3. This theory is justified as the Symbiote Spider-Man: King in Black Vol 1 to 5 comic series established that the Hive-Mind transcends space and time.
With rumors about Knull's appearance in future Venom movies, it is plausible that Spider-Man could join Venom to help save the universe against Knull.
There is also speculation that Sony might give more standalone projects to Tobey Maguire and Andrew Garfield as Spider-Man. This would make it possible for any of the Spider-Men to accompany Venom and Eddie against Knull.