What does 1.5TB mean?

1,5TB means 1,5 Terrabyte.

A terrabyte is 1000GigaByte. A "byte" is a value that we use to calculate memory with, the more bytes a computer have, the more memory it has. If for instance a harddrive has 1,5TB it has appr. 1,46TB (or appr. 0.0014PT) available memory that the user can use to store data on.

1.5TB is a lot of memory per average personal use 2010.