Hello, anon-private, and welcome.
I have split your question from the other thread where you had posted, as this is in fact a different question and topic from that.
I have also given it another title to avoid confusion.
Download is, as you surmise, all that you invite on to your PC whilst connected to the internet, and will include such as emails, security prog. updates, and the cache of web pages accrued during normal browsing..........all fairly light usage stuff.
Heavier download usage will include any file sharing, P2P stuff, video streaming, on-line gaming etc etc.