It’s a term to indicate that a person will look at the behavior of the rest of the people in the surroundings before acting or doing something, especially in the times of uncertainty.
There was an experiment done in psychology on social proof . It goes something like this:
“..one or more …

Never reject yourself before others reject you.
“I will never apply for that job in that super awesome company because I know I don’t have the qualifications.”
“I don’t think I will apply to that top school because I am just not smart enough.”
“I don’t know. I don’t think I will register …