What's the difference between lossy and lossless?

Related questions

1. Which compressions provide some loss of quality?
2. When would you use lossy compression?
3. How do I decrease the size of a GIF?
4. How do I reduce a JPG file size?
5. How do I make a boomerang video?
6. How do I compress a JPEG online?
7. Does compressing a photo reduce quality?
8. How do I compress a JPEG to 100kb?
9. What is the size of 50 KB photo?
10. Is JPG lossy or lossless?

Tags

1. #means
2. #worse
3. #removes
4. #decompressed
5. #remains
6. #original
7. #compressed
8. #permanently
9. #picture
10. #compression
11. #quality
12. #lossy
13. #lossless