The Spanish t and the English "t" are pronounced much alike, but there is a subtle difference. In Spanish, the t is typically pronounced with the tongue touching the top teeth, while in English the tongue typically touches the roof of the mouth. As a result, the Spanish t is softer or less explosive than the "t" in English usually is. The "t" in a word such as "stop" is quite close in sound to the t of Spanish.
In our audio lesson on pronouncing the t, you can hear the English word "tea" followed by the Spanish ti (a personal pronoun meaning "you") to note the difference. You can also hear the word señorita, a courtesy title for a young woman.