When you practice tolerance, you accept another's ideas and beliefs. If you respect someone's opinions — even if you disagree or find them nonsensical — you display tolerance.
The noun tolerance, which stems from the Latin for "endurance," also refers to an organism's ability to stand or handle a difficult environmental condition. If you build up a tolerance, you can handle large amounts of something (from medicine to psychological abuse) without being too strongly affected. We usually use the word to refer to our need to accept others, as suggested by John F. Kennedy when he said, “Tolerance implies no lack of commitment to one's own beliefs. Rather it condemns the oppression or persecution of others.”