Net PP&E is short for Net Property Plant and Equipment. Property Plant and Equipment is the value of all buildings, land, furniture, and other physical capital that a business has purchased to run its business. The term "Net" means that it is "Net" of accumulated depreciation expenses.
For example, assume that a company buys a building worth $1,000,000, along with $50,000 of furniture. Their Net PP&E at the moment of purchase is $1,050,000.
Each year, however, the company must depreciate the value of that PP&E to account for the fact that it will wear out an need to be fixed or re-purchased in the future. Assume that in the first year, the company depreciates the building and furniture by $105,000 (or 10% of the original value). Then, at the end of the year, its Net PP&E is:
$1,050,000 - $105,000 = $945,000
As the company buys more PP&E, the value of its Net PP&E will increase, and as time passes, the value will decrease according to depreciation expenses.