system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes a password stronger than another?

How is a password that has uppercase and lowercase letters, numbers, and special characters more secure if every character is always a possibility?
gpt
Because some types of attacks will do what's called a 'dictionary attack' and try dictionary words and thing based on them (apple, Apple, APPLE, etc).  If you have to brute force a password (meaning try every possible combination) then as you add numbers, case, and specials the number of possible combinations goes through the roof (keep in mind, on average you'd have to try 50% of the possible combinations to get it right).

Having those all be possible characters in a password increases the amount of possible passwords and hence makes it hard to guess.