Many people misunderstand what socialization means. The 1 sentence definition is: Socialization means giving your dog positive experiences and having them focus on you in any environment or situation. Here is a great article on socialization that applies to both puppies and adult dogs, even rescues:

Here is a 5min video that goes along with this article.

Socialization is a long-term investment in your puppy. EVERYONE loves your puppy, but it’s up to you to protect them. As much as all of us want to run right up to them and have our 30min of cuddling or play, we’ll go home afterwards and you’ll be with the puppy for the next 10-15 years. Your dog’s experience and safety need to be your #1 priority. Bad experiences, particularly between 8 and 12 weeks of age, can shape their behavior for the rest of their life.

Here is a pretty exhaustive list of environments, surfaces and things to ensure your puppy encounters and does OK with. There are a few variations on this out there, but the idea should be clear. Ensure they encounter as a puppy and IGNORE everything you expect them to handle gracefully as an adult: