It's different. Cat is a word that begins with a T. When you pronounce it, you need to put your tongue between your upper and lower teeth, and then make a T sound. This sound is produced by the airflow between your tongue and your teeth. Air flows from the tip of the tongue, and then goes up through the upper jaw to form a crisp T-sound, while eat is a word with the beginning of e. When you pronounce it, you need to put your tongue in the middle of your mouth, then lift it to the upper jaw to make a slightly vague E-sound, and then move your tongue backwards.