Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a very strange animated television series about a girl named Fionna and her cat Cake who embark on quests through the multiverse to bring magic to their mundane world. In this episode, Fiona and Cake and Dr. Simon Petrikov are hunting for a magic crown that can turn him into the Ice King again.
We don't see Fionna or Cake in this scene. It's a flashback illustrating a story Petrikov tells Fionna about how he and his wife Betty met, then went on an expedition to search for an ancient book called the Enchiridion. We see them walking outdoors in a rocky area when he hears hissing and stops. He tells her there are snakes in the area - Horned Vipers. He continues walking, poking the ground with his walking stick to alert the snakes. She offers to clear the path using a trick her mom taught her, but he wants to use his walking stick instead. She decides to do it her way anyway, and we learn that her mother's way is to run, waving her arms and shouting gibberish to flush out the snakes, and it works. We see several snakes crawl out of the rocks and off the path and Petrikov is impressed.
Fionna's method is a bad one, because the snakes come out of hiding after she passes them, leaving the possibility she could still step on one, and when the snakes are scared and flushed out, they would be upset and defensive and prone to bite Petrikov. (There's an old joke about hiking in snake country: The first person walking past the snake startles it. The second person walking by makes it angry. The third person is the one it bites.) But it's not meant to be a good idea, it's meant to be funny and to show that she's young and impulsive.
When we see the unusual tails on the snakes, it's obvious that they are supposed to be a very unusual rare species - the Spider-tailed Horned Viper, Pseudocerastes urichoides, native to a small region of Iran and Iraq. The most interesting thing about these vipers is how they use their tails to imitate spiders to lure their spider-eating prey, but we don't see that in this scene.