HT Games
You're likely comparing the Xbox 360 (2005) and the Xbox One (2013).
| Console | Width | Depth | Height | Volume |
|---|---|---|---|---|
| Xbox 360 (Slim) | 270 mm | 264 mm | 75 mm | ~5.3 L |
| Xbox One (Original) | 333 mm | 274 mm | 79 mm | ~7.2 L |
The Xbox One is ~35% larger by volume than the Xbox 360 S/E.
"Xbox" is the brand. "Xbox One" is the third console. People often say "Xbox" meaning the original 2001 console (which is even larger than the One).