Tension can take on many forms and has many valuable purposes. Tension can nudge the reader into anger or frustration. It can make a reader yell at the characters in your story. Most importantly, it will cause them to read on with the characters until the conflict is resolved.
To create tension, Steinbeck went against the character(s) personality; he made someone seem out of place in the surroundings, he created some conflict, he made challenge a struggle and a struggle a challenge (everything was complicated and messed up), he used colloquial speech to suggest disagreements, he created something funny going on at the same time as something sad, he created something unimportant going on at the same time as something important, he had the characters share a dirty little secret and then threaten to have it revealed.
Steinbeck also created confusion between the characters. He made the situation so chaotic that the characters not only did not understand the situation, but also did not know what to do. E.g. ‘Curley had punched Lennie because he thought he saw Lennie laugh at him, little did he know, Lennie was only fanaticizing about taming rabbits on their future farm, Lennie was just standing there yelling for George to tell Curley to stop hitting him.’ After Steinbeck used confusion to create tension, he added in urgency. This made the already tense situation unbearable. E.g. ‘George told Lennie to hit Curley