Negative film records the image with tones inverted (color negatives add the orange mask on top). You only see the final picture after printing or scanning inverts it back. Its greatest strength is exposure latitude: a stop or two of error is recoverable, which makes it ideal for beginners.
Reversal (slide) film develops directly into a positive. On a light table, the transparency and color intensity are unlike anything else. But the exposure latitude is razor thin (about ±0.5 stop), demanding accurate metering and technique.
Starting out? Shoot color negative (C41). Once your exposure is confident, treat yourself to the E6 reversal experience.